The Eri B. Sitt Edition and Audio Series of the Talmud Bavli, Tractate Rosh Hashanah, has been sponsored by Mr. Solly and Cheryl Mizrahi, may God grant them life and peace, for the success of both of their families. May they enjoy, with God’s help, health, happiness, continued success, and much pleasure from their children. In the merit of their dedication to Tractate Rosh Hashanah, may they merit good judgment, good blessing, and success in all their endeavors. Amen.
Today’s page, 19, is dedicated in memory of Shoshana bat Atara, by her son, Obaja Musali. May her soul be bound in the bonds of eternal life. Amen. Today’s page is also being studied for the elevation of the soul of Avraham ben Esther. May his soul rest in the Garden of Eden. Amen. It is also being studied for the elevation of the soul of Acham Yaakov Katsin ben Altun. May his soul rest in the Garden of Eden. Amen. Finally, it is being studied for the complete recovery of Eliyahu Hayim ben Shafiah. May God send him a complete recovery of body and soul.
We begin today’s page, 19, at the very top. First, let us introduce the subject so that we understand precisely where we are entering today’s discussion.
Yesterday, we learned about a scroll that existed during the time of the Temple. That scroll was called Megillat Ta’anit. Ironically, Megillat Ta’anit contains all the dates on which one is not permitted to fast, because different miracles happened to the Jewish people on those days. Some of those days were so special that the Sages said one was not permitted to eulogize on them either.
There is, however, a major dispute among the Sages about what happened after the destruction of the Temple. Did Megillat Ta’anit remain in effect, or not? One line of reasoning says that it did not remain in effect. We know that the four fast days—the Seventeenth of Tammuz, the Tenth of Tevet, the Fast of Gedaliah, and Tisha B’Av—were, when the Temple stood, considered days of happiness and rejoicing. Once the Temple was destroyed, they reverted to being fast days. According to this reasoning, just as those days reverted from days of happiness to fast days, the days recorded in Megillat Ta’anit, which had originally been holidays, could also revert to days on which fasting was permitted, if the Sages deemed it appropriate.
Another opinion says that only the days explicitly mentioned in the verse—the fast of the fourth month, the fast of the fifth month, the fast of the seventh month, and the fast of the tenth month—revert after the destruction of the Temple. Megillat Ta’anit, however, remains in effect even after the destruction, and the dates listed there remain holidays.
The Gemara then brought a challenge. There was a certain day, the third of Tishrei, on which the Sages instituted a significant ruling: from that point onward, God’s Name could no longer be written in legal documents.
Why had God’s Name been written in those documents in the first place? When the Greeks ruled over the Jewish people, they decreed that the Jews were not permitted even to mention God’s Name verbally. Anyone who mentioned it was punished. When the Hasmoneans arose and defeated the Greeks, they went to the opposite extreme. They said that not only would God’s Name once again be mentioned verbally, but that a new enactment would be made: whenever a person wrote a legal document—for example, when one person lent money to another—the document would include God’s Name.
The documents were dated in this manner. For example, they might say, “This document was written in the fourth year of Yohanan the High Priest, to the exalted God.” Thus, the word referring to God’s exalted status would be written in the document. This was the enactment of the Hasmoneans, and the practice became widespread. Everyone began putting God’s Name into legal documents.
The Sages strongly opposed this enactment. Although it had been instituted by the Hasmoneans, the Sages wanted it uprooted. They were concerned because they understood what would eventually happen to such documents. Once a person paid the debt recorded in the document, what would he do with it? He would tear it up and throw it into the garbage. If God’s Name were written there, it would ultimately be treated disrespectfully.
Ordinarily, when a custom becomes deeply established among the people, it is not simple to uproot it. Nevertheless, the Sages were miraculously successful—Rashi describes it as a miracle—and on the third of Tishrei they were able to uproot the practice. The people accepted that they would stop writing God’s Name in legal documents. The Sages felt that this was such a momentous day that they declared it a holiday on which fasting would not be permitted.
Now, before we proceed, the Sages raised a question. If this enactment took place after the destruction of the Temple, and if the dates recorded in Megillat Ta’anit had already been nullified, how could the Sages add a new date? If the original dates had been nullified, they should not have added additional ones. The fact that they added another date seems to prove that Megillat Ta’anit was still in effect after the destruction of the Temple.
The Gemara answers that this is not a proof. The story did not take place after the destruction of the Temple. It occurred while the Temple was still standing. At that time, everyone agrees that Megillat Ta’anit was in effect, and therefore it was certainly possible to add another date to it.
The Gemara now begins: “If so, what is the purpose of this date? It is the day on which Gedaliah ben Ahikam was killed.” If the incident took place while the Temple was standing, there is no need for Megillat Ta’anit to make the third of Tishrei a holiday. The third of Tishrei was already a holiday, because it was the date of the Fast of Gedaliah. During the period of destruction, it was a fast day, but what was its status once the Temple was rebuilt? All those fast days reverted to being holidays. The third of Tishrei, then, was already a holiday in any event. What benefit was there in adding it to Megillat Ta’anit?
Rav said that Megillat Ta’anit was needed to prohibit fasting on the day before as well. The innovation of including the date in Megillat Ta’anit was that not only would fasting be prohibited on the third of Tishrei, but it would also be prohibited on the second of Tishrei.
The Gemara objects that there is already an established rule that one may not fast on Rosh Chodesh, and that fasting is also prohibited on the day after Rosh Chodesh. Since Rosh Chodesh is the first of Tishrei, the second of Tishrei is already prohibited as the day after Rosh Chodesh. Why, then, is there any need to tell us that the day before the third of Tishrei is prohibited?
The Gemara answers that Rosh Chodesh is a Torah law, and Torah laws do not require reinforcement. The reason the Sages prohibited the day before a date recorded in Megillat Ta’anit is that those dates are rabbinic enactments. People tend to treat rabbinic laws lightly, so the Sages strengthened their enactments by prohibiting fasting on the preceding day as well. When people hear that they may not fast not only on the holiday itself but also on the day before it, they understand that the rabbinic enactment must be taken seriously.
Torah laws, however, do not require such reinforcement. People already approach a Torah law with fear and seriousness. Therefore, if the prohibition were based only on Rosh Chodesh, there would be no need to prohibit the following day. The second of Tishrei would ordinarily be permitted, and it is prohibited only because the Sages included the third of Tishrei in Megillat Ta’anit. Since that holiday is rabbinic in nature, the Sages reinforced it by prohibiting the preceding day as well.
This is taught in a baraita: The days written in Megillat Ta’anit are prohibited for fasting both on the day before them and on the day after them. Shabbat and the holidays, however, are themselves prohibited for fasting, but fasting is not prohibited on the days before or after them. What is the distinction? Shabbat and the holidays are rooted in Torah law, and Torah law does not require reinforcement. The days of Megillat Ta’anit are rabbinic, and rabbinic enactments do require reinforcement.
We therefore return to the original proof. Megillat Ta’anit was in effect, and the innovation was that although the third of Tishrei was already a holiday because it had previously been the Fast of Gedaliah, adding it to Megillat Ta’anit prohibited the second of Tishrei as well.
The Gemara then raises another question. The day before the third of Tishrei should already be prohibited because it is the day after Rosh Chodesh. The Gemara answers that this is not so. A Torah law does not require reinforcement, and the enactment concerning Rosh Chodesh is treated like a Torah law. Nor could the prohibition of the preceding day be based on the Fast of Gedaliah, because that enactment was made by the prophets and therefore has the status of Torah law for this purpose. It also does not require reinforcement. The only reason the second of Tishrei is prohibited is that the third of Tishrei was included in Megillat Ta’anit. Once it is a rabbinic holiday, the Sages prohibit the day before it as well.
Thus, Megillat Ta’anit had a purpose: it was necessary for the Sages to institute the holiday of the third of Tishrei in order to prohibit the second of Tishrei too.
Rav Tubi bar Matana then raised a question. On the twenty-eighth of Adar, good news came to the Jewish people: they would no longer be prevented from studying Torah. The wicked government had decreed that the Jewish people were not permitted to study Torah, circumcise their sons, or observe the commandments.
What did Yehudah ben Shamuah and his colleagues do? They went to a certain prominent woman. The important Roman political figures used to gather in her home, and she therefore had a good understanding of what was happening within the government. They approached her to ask whether she could advise them how to overturn the decree.
She told them, “Go out tonight and cry in the marketplaces, so that the Roman officials will hear your cries and have mercy on you.” Following her advice, the Sages went out at night to the area where the Roman officials were present, and they cried out: “For the sake of Heaven, are we not your brothers? You come from Esau and we come from Jacob. Are Jacob and Esau not brothers? Do we not come from the same father? Do we not have the same lineage? Are we not descended from the same mother, Rebecca, who carried Jacob and Esau in her womb? Why do you treat us differently from every other nation? Why do you single us out and impose all these decrees upon us?”
When the Romans heard the cries of the Sages, compassion entered their hearts. They took pity on the Jewish people and nullified the decree. The Sages then declared that the twenty-eighth of Adar would be a holiday on which fasting was prohibited.
Rav Tubi bar Matana asked: If Megillat Ta’anit had been nullified, how could the Sages add a new date? The original dates had been nullified, and now they were adding new ones.
The Gemara answers that perhaps the incident occurred while the Temple was still standing. At that time, everyone agrees that Megillat Ta’anit was in effect. The Gemara rejects this possibility. We know that the incident could not have occurred while the Temple was standing, because the Sage responsible for the miracle was Yehudah ben Shamuah, and Yehudah ben Shamuah was a student of Rabbi Meir.
We know that Rabbi Meir lived after the destruction of the Temple. Rashi explains the chronology. The Temple was destroyed during the time of Rabbi Yohanan ben Zakkai. Rabbi Eliezer was a student of Rabbi Yohanan ben Zakkai, Rabbi Akiva was a student of Rabbi Eliezer, and Rabbi Meir was a student of Rabbi Akiva. Thus, several generations had already passed by the time of Rabbi Meir, and certainly the Temple had been destroyed. Yehudah ben Shamuah, being a student of Rabbi Meir, lived after the destruction as well.
The Gemara now proves that Yehudah ben Shamuah was a student of Rabbi Meir. At the bottom of the page, we have a Mishnah concerning a glass vessel. As long as the glass vessel is intact, it is susceptible to ritual impurity. For example, if a dead rodent falls upon it, or if it is located in a house containing a source of impurity, the vessel can become impure.
How does a glass vessel lose its impurity? There are two possibilities. One may immerse it in a ritual bath, or it may break. When it breaks, it becomes pure, like an earthenware vessel. The law of an earthenware vessel is that its breaking purifies it.
The Mishnah discusses a glass vessel that became impure and then developed a hole. The owner took lead and sealed the hole. The vessel was now complete again. Rashbag, Rabban Shimon ben Gamliel, said in the name of Rabban Shamuah that the vessel was impure. The Gemara identifies Rabban Shamuah as Yehudah ben Shamuah and says that this proves Yehudah ben Shamuah was a student of Rabbi Meir.
What is the basis of the ruling? Ordinarily, once a vessel breaks, its impurity disappears. If one repairs it, the original impurity does not return. This is called the return of impurity, and we generally do not say that the previous impurity returns.
There is, however, a special law concerning metal vessels. If a metal vessel was intact and impure, then broke and was repaired, its impurity returns. The vessel under discussion is made of glass, not metal. Nevertheless, since it was repaired with lead, and the lead is what holds the vessel together, the glass vessel is considered to have the status of a metal vessel. Therefore, the impurity returns.
This is the principle of the supporting component. The supporting component is the element that holds the vessel together. Since the glass vessel is being sustained by a piece of metal, Rabbi Meir rules that it has the legal status of a metal vessel. Metal vessels are subject to the return of impurity, and this glass vessel is treated the same way because of the metal supporting it.
Rashi explains that the old impurity returns. The vessel did not come into contact with a new source of impurity; rather, the original impurity returned. Although glass vessels do not ordinarily have this law, the lead sustains the vessel, and therefore it is considered like metal. Everything follows the supporting component.
What have we learned from this? We have learned that Rabbi Meir was the teacher of Yehudah ben Shamuah. Since Yehudah ben Shamuah lived after the destruction of the Temple, and the Sages established the twenty-eighth of Adar as a holiday during his time, it follows that Megillat Ta’anit was still in effect after the destruction. Not only did the existing dates remain in force; new dates could also be added.
Incidentally, regarding the vessel that broke and was repaired with lead, the Sages disagree. They say that the glass vessel is pure. We follow the majority of the vessel. Since most of it is glass, we do not follow the lead merely because it is the component holding the vessel together.
The Gemara now returns to the question of whether Megillat Ta’anit remained in effect after the destruction of the Temple. In fact, this issue is itself a dispute among the Tannaim. A baraita teaches: “These days written in Megillat Ta’anit are prohibited,” whether the Temple is standing or whether the Temple is not standing. This is the position of Rabbi Meir. We have now found the first Tanna who says that Megillat Ta’anit was not nullified, even after the destruction.
Rabbi Yosei, however, says that when the Temple is standing, the dates are prohibited for fasting because they are days of happiness. Once the Temple was destroyed, the dates became permissible for fasting, because there was no longer a Temple, and those days could revert to becoming fast days.
What is the final law? One tradition says that the law is that the dates were nullified. Another tradition says that the law is that they were not nullified. This seems contradictory. In one place, the law is that Megillat Ta’anit was nullified; in another place, the law is that it was not nullified.
The Gemara answers that the two statements are referring to different categories. With regard to Hanukkah and Purim, which are among the days mentioned in Megillat Ta’anit, the law is that they were not nullified. Even after the destruction of the Temple, Hanukkah and Purim remain holidays on which one may neither fast nor eulogize.
Every other date in Megillat Ta’anit, however, could revert to becoming a potential fast day. Thus, when one tradition says that the law is that Megillat Ta’anit was nullified, it refers to all the other dates. When the other tradition says that the law is that it was not nullified, it refers to Hanukkah and Purim, the only two dates from Megillat Ta’anit that retain practical significance today. One may not fast or eulogize on those two holidays.
For example, if someone wished to establish a fast on the twenty-eighth of Adar, the date of the miracle we discussed, that would be possible today. Megillat Ta’anit was nullified for practical purposes after the destruction of the Temple, except with regard to Hanukkah and Purim.
The Gemara then returns to our Mishnah, which taught that messengers were sent to inform the people in Babylonia and the other areas of the Diaspora when Rosh Chodesh Elul had been established. Why was it important for them to know when Rosh Chodesh Elul was? So that they would know when to observe Rosh Hashanah.
Rosh Hashanah is at the beginning of the month, so there was no way to send messengers after Rosh Chodesh Tishrei to inform the Diaspora in time. By the time the messengers arrived, Rosh Hashanah would already be over. Therefore, they sent messengers one month earlier, in Elul.
Most of the time, Elul had twenty-nine days. Once the people knew when Rosh Chodesh Elul was, they would count twenty-nine days. On the thirtieth day, they would establish Rosh Hashanah. As we learned yesterday, they would actually observe two days of Rosh Hashanah—the thirtieth day and the following day—to ensure that they observed it on the correct date.
Messengers were also sent to inform the Diaspora when Rosh Chodesh Tishrei had been established, so that the people would know the correct date of Yom Kippur and Sukkot. The people were understandably concerned. They did not know whether they were observing Yom Kippur on the correct day, and they did not know whether they were observing Sukkot on the correct day. The Sages therefore said that messengers should be sent out in Tishrei. Whatever the people had done for Rosh Hashanah, they had already done; but they would then know the correct dates for the upcoming holidays.
The Gemara asks: Once messengers were sent in Elul, why was it necessary to send them in Tishrei as well? Once the people knew the date of Rosh Chodesh Elul, they would count twenty-nine days, and the thirtieth day would be Rosh Hashanah. They would then continue counting and know when Yom Kippur and Sukkot would occur.
The Gemara answers that it was not because an extra day of Elul had actually been found. From the time of Ezra, Elul had never been extended to thirty days. Therefore, once the people knew the beginning of Elul, they automatically knew the dates of the subsequent holidays.
Nevertheless, if a need had arisen, Elul could have been extended. The Gemara is not saying that the Sages never would have done so; it is saying only that the need never arose. If there had been a need, they would have added an extra day to Elul, and then it would have been necessary to send messengers in Tishrei so that the people would know the actual dates of Yom Kippur and Sukkot.
What would that need have been? The commentators later explain two possible reasons. The Sages did not want Yom Kippur to fall on a Sunday, immediately after Shabbat.
One reason concerned the vegetables needed to break the fast. If Yom Kippur were on Sunday, the people would have to prepare the vegetables on Friday, because they could not prepare them on Shabbat. After Shabbat and Yom Kippur, by Sunday night, the vegetables might already be spoiled.
Another reason concerned the burial of the dead, God forbid. One may not bury someone on Shabbat, and one may not bury someone on Yom Kippur. If a person died on Shabbat or on Friday immediately before Yom Kippur, the burial could be delayed for two days, until Monday. Therefore, the Sages always tried to create a separation between Shabbat and Yom Kippur.
In such a situation, they would add an extra day to Elul to prevent these problems. We therefore see that it was possible to extend Elul. Since they could add an extra day, it was necessary to send messengers in Tishrei so that the people would know the actual dates of Yom Kippur and Sukkot.
The Gemara asks what would happen if Elul were extended. The people in the Diaspora would have celebrated the wrong day of Rosh Hashanah. They followed the rule that Elul had twenty-nine days. They counted from Rosh Chodesh Elul, and on the thirtieth day they observed Rosh Hashanah. If the Sages added an extra day to Elul, the thirtieth day would not actually be Rosh Hashanah; Rosh Hashanah would be the following day.
The Gemara gives an extraordinary answer: It is preferable to allow Rosh Hashanah to be disrupted if necessary, so long as the other holidays can be established at the correct time. If the Sages could ensure that Yom Kippur and Sukkot would occur on the correct dates, they considered that more important, even though the people in the Diaspora might observe Rosh Hashanah on the wrong day.
It was suggested that perhaps the two-day observance of Rosh Hashanah would solve the problem. The answer is that this depends on the opinion that Rosh Hashanah was observed for two days. According to Rashi, it appears that the issue was that they observed only one day.
The Gemara brings a proof from our Mishnah that the Sages were concerned about the holidays occurring at the correct time. The Mishnah says that messengers were sent in Tishrei for the purpose of establishing the dates of the holidays. Why would that be necessary if the date had already been determined in Elul? It must be because Elul could be extended. Since an extra day could be added to Elul, the dates of the holidays could fluctuate. The fact that the Mishnah says messengers were sent in Tishrei shows that the Sages were more concerned with establishing the holidays at the proper time than with ensuring that Rosh Hashanah was observed on the correct day in the Diaspora.
The Mishnah further teaches that messengers were sent in Kislev because of Hanukkah and in Adar because of Purim, so that the people would know precisely when to observe those holidays.
The Gemara asks: If the Sages added an extra month of Adar to the year, which month would be used for Purim—the first Adar or the second? And in which Adar would messengers be sent?
The Gemara initially observes that the Mishnah does not mention the case of a leap year. It states that messengers were sent in Adar because of Purim, but it does not say that in a year with two Adars they were sent in the second Adar. This seems to imply that they were sent only in the first Adar, even in a leap year. If the Mishnah intended to teach that messengers were sent in the second Adar, it should have stated that explicitly.
Accordingly, the Gemara initially suggests that the dispute is whether Purim is observed in the first Adar or the second Adar. Our Mishnah would hold that Purim may be observed in the first Adar, so there would be no reason to send messengers in the second Adar. Rabbi holds that Purim is observed in the second Adar, which is why messengers would need to be sent then.
The Gemara asks whether this is truly the dispute. One opinion could say that all commandments applicable in the second Adar may be observed in the first Adar. According to that opinion, Purim could be observed in the first Adar. The other opinion could say that commandments applicable in the second Adar cannot be observed in the first Adar, so Purim must be observed in the second.
A question was raised: Even if the issue is only when Purim is observed, should messengers not be sent merely to inform the people that there is a second Adar? The Tosafot answer that this is unnecessary. Messengers are sent in Nisan as well. If the people in the Diaspora do not receive the message in Nisan when they expect it, they will automatically understand that there were two months of Adar.
The Gemara then wishes to say that the dispute concerns whether commandments that apply in the second Adar may be observed in the first. According to the opinion that they may be observed in the first, Purim is celebrated in the first Adar, and no messengers need to be sent in the second. According to the opinion that they may not be observed in the first, Purim must be celebrated in the second, and messengers must be sent in the second.
The Gemara reviews the discussion. The Mishnah listed six months in which messengers were sent to inform the people in the Diaspora when Rosh Chodesh had been established. One of those months was Adar, because the people needed to know when Purim would be. The Gemara then asks why the Mishnah did not say that in a leap year messengers must be sent in the second Adar. It initially concludes that the Mishnah must hold that Purim can be observed in the first Adar.
The Gemara rejects that conclusion. Everyone may agree that Purim is observed only in the second Adar. The dispute may instead concern the mechanics of a leap year.
A baraita teaches that when a leap year is established, the first Adar may contain either thirty days or twenty-nine days, depending on the opinion. According to one opinion, the first Adar is always a full month of thirty days, and the second Adar begins on the thirty-first day. According to another opinion, the first Adar is a regular month of twenty-nine days, and the second Adar begins on the thirtieth day.
The Gemara initially reasons that this may explain why messengers do not need to be sent in the second Adar. Once the people know when the first Adar began, they can count the appropriate number of days. According to the opinion that the first Adar always has thirty days, they count thirty days, and the thirty-first day is the beginning of the second Adar. According to the opinion that the first Adar has twenty-nine days, they count twenty-nine days, and the thirtieth day is the beginning of the second Adar. In either case, the date would seem to be known automatically.
The Gemara objects that if the people can determine the date when the first Adar has thirty days, they should likewise be able to determine it when the first Adar has twenty-nine days. Why should there be a dispute about whether messengers must be sent?
Rav Pappa answers that the opinion referring to a month does not mean that the first Adar always has twenty-nine days. It means that the first Adar may have either twenty-nine or thirty days. Since it can fluctuate between the two possibilities, messengers must be sent to inform the people precisely when the second Adar begins. According to the other opinion, the first Adar always has thirty days, so there is no uncertainty. Once the people know the beginning of the first Adar, they can simply count thirty days, and the following day is the beginning of the second Adar.
Rabbi Yehoshua ben Levi testified in the name of the holy congregation of Jerusalem regarding the two months of Adar. When there are two Adars, Rosh Chodesh is established on the thirtieth day of each one. The thirtieth day is called the added day, because it is the day added to a month that otherwise consists of twenty-nine days.
This testimony implies that both Adars are always deficient months of twenty-nine days, with the thirtieth day becoming Rosh Chodesh. One never makes either Adar a full month of thirty days, because then Rosh Chodesh would occur on the thirty-first day.
The Gemara challenges this from a teaching of Rav Simai in the name of Haggai, Zechariah, and Malachi. Regarding the two months of Adar, they taught that if the Sages wished to make both months full, they could do so; if they wished to make both months deficient, they could do so; and if they wished to make one deficient and one full, they could do so. This differs from the earlier testimony, which indicated that both Adars must be deficient.
We therefore have a significant dispute concerning the structure of the two Adars. The first opinion says that both are always deficient, and that the thirtieth day is Rosh Chodesh for both the first and second Adar. The testimony in the name of the prophets, however, says that the structure is flexible: both may be full, both may be deficient, or one may be deficient and the other full.
In the name of Rabbeinu—whom Rashi identifies as Rav—the Gemara says that in the Diaspora, the practice concerning the two Adars was to make one month deficient and the other full, until word arrived from the Land of Israel telling them exactly what had been established.
The Gemara also teaches that the Adar closest to Nisan, which is the second Adar, is always deficient. This provides another general rule: the Adar immediately preceding Nisan always has twenty-nine days.
Rav Nachman then raised a question. There are two months of the year in which the messengers are permitted to desecrate Shabbat in order to reach their destination: Nisan and Tishrei. Normally, one may travel only within the Shabbat boundary, but regarding these two months, the witnesses are permitted to travel beyond that boundary. These are the key months because the people must know the date of Passover in Nisan, and in Tishrei they must know the dates of Yom Kippur and Sukkot.
Rav Nachman asks: If the last Adar sometimes has twenty-nine days and sometimes thirty days, we understand why the witnesses must be allowed to travel on Shabbat. The people need to know whether the month of Nisan begins on one day or the next. But if the last Adar is always deficient, as the teaching of Mar Ukva indicates, why is it necessary to allow the witnesses to desecrate Shabbat for Nisan?
Once the people know when Rosh Chodesh Adar was established, and once they know that the final Adar always has twenty-nine days, they can count twenty-nine days. The following day will be Rosh Chodesh Nisan, and they will automatically know when Passover occurs. Why, then, is it necessary to rush the witnesses and permit them to travel on Shabbat?
The Gemara gives the final answer: It is because of the special mitzvah of sanctifying the month based on the testimony of witnesses. The verse says that this month shall be for you the beginning of months. Moses was shown the new moon by God, and God indicated that when the witnesses see the moon in that manner, they should sanctify the month. Thus, there is a mitzvah to sanctify the month according to the testimony of witnesses.
At this point, I want to correct one detail. When we said that Shabbat may be desecrated, we were referring to the witnesses who come to the court in Jerusalem to testify that they saw the new moon—not to the messengers who travel to the Diaspora.
Normally, if those witnesses must leave the Shabbat boundary in order to reach the court, we tell them not to travel. The court can establish Rosh Chodesh automatically. If the witnesses do not arrive by a certain time, the court sanctifies the month by default. There are, however, two months in which the witnesses who saw the new moon are told to desecrate Shabbat and reach the court. Those months are Nisan and Tishrei.
But the question remains. Why must the witnesses travel for Nisan? If Adar is always twenty-nine days, the court will automatically establish Rosh Chodesh Nisan on the thirtieth day. Whether the witnesses arrive or not, the court knows that on that day the month must be sanctified. Why, then, is there such urgency to bring the witnesses?
The Gemara answers that although the court can sanctify the month automatically, it is preferable to do so through the witnesses. There is a mitzvah to hear their testimony and declare that the month has been sanctified. The verse teaches that the month should be sanctified in this manner, through the testimony of those who saw the new moon.
The Sfat Emet asks a further question. According to this explanation, if there is a mitzvah in every month to sanctify the month through the testimony of witnesses, then witnesses should be permitted to desecrate Shabbat during all twelve months of the year. Why does the Mishnah mention only Nisan and Tishrei?
He answers that for every month there is indeed a mitzvah to sanctify the month through the testimony of witnesses. However, Shabbat may be desecrated only when doing so serves a correction for the holidays, such as ensuring that the holidays will occur at the proper time and that the offerings can be brought.