When considering the status of an animal's offspring as a firstborn, a crucial factor is whether the mother has given birth previously. If an animal's prior birthing history is unknown, its offspring's status as a firstborn becomes a matter of doubt, a safek. The discussion then turns to the age at which different animals typically reach maturity and begin to bear young, as this age can help determine if a birth is likely a firstborn or not.
For instance, regarding a goat, the opinion of Rabbi Yishmael is that if a goat is one year old, it is certain (vadai) that it has not given birth yet. Therefore, any offspring born to it at this age would definitively be a firstborn, requiring it to be given to a Kohen. However, if the goat is older than one year, its birthing history becomes uncertain, making any subsequent offspring a safek. In such a case of doubt, the animal is allowed to graze, and its owners may eventually consume it, as it is not definitively a firstborn. Similarly, for a sheep, maturity is generally reached at two years old; thus, offspring born before this age are considered vadai firstborn, while those born after are a safek. For a cow or a donkey, the cutoff age for a vadai firstborn is three years old.
Rabbi Akiva challenges Rabbi Yishmael's certainty. While acknowledging that a one-year-old goat may not have had a viable birth, Rabbi Akiva introduces the possibility of a miscarriage. A miscarriage also exempts subsequent offspring from the status of a firstborn. Therefore, even if an animal is under the age where it typically gives birth, it might have had a miscarriage, rendering any subsequent birth a safek, not a vadai firstborn. Miscarriages have discernible signs, such as a dirty secretion (tinuf) in smaller animals or the expulsion of a placenta or embryonic sac in larger animals.
The Mishnah presents a general rule from Rabbi Akiva: if it is known with certainty that an animal has given birth before, its offspring is not a firstborn. If it is known with certainty that it has not given birth, its offspring is a firstborn and goes to the Kohen. If there is a safek, the animal is allowed to graze until it develops a blemish, at which point the owners may eat it.
The Gemara then questions the Mishnah's ruling that offspring born after the typical maturity age are a safek. Why not follow the majority (rov) of animals, which typically give birth within their first year? If the majority of animals give birth within their first year, then an animal acquired after its first year should be presumed to have already given birth, making its new offspring not a firstborn. This would mean it is not a safek, but rather definitively not a firstborn. The Gemara suggests that perhaps Rabbi Yishmael follows the approach of Rabbi Meir, who is known to be concerned even for a minority (chayish l'mi'uta). If so, even if a majority of animals give birth within the first year, Rabbi Yishmael would be concerned about the minority that do not, thus creating a safek.
However, the Gemara prefers to interpret the Mishnah as consistent with the general rabbinic view, which usually follows the majority. The rabbis follow the majority when the majority is "before us" (itah kaman), meaning observable and quantifiable in a specific situation. Examples include nine kosher stores out of ten, or a vote in a Sanhedrin. In such cases, the majority is followed. But when it comes to a statistical majority that is not directly observable, such as the general statistic that most animals give birth within their first year, the rabbis do not necessarily rely on it. This type of statistical majority is considered "arbitrary numbers" and not "before us." Therefore, the Mishnah, even according to the rabbis, would treat the offspring as a safek, as the birthing history is not directly observable.
The Gemara further explores the concept of being concerned for a minority through a case involving chalitzah (a ceremony performed when a man dies childless and his brother refuses to marry his widow) and yibum (levirate marriage). According to Rabbi Meir, if either the man or the woman is a minor, neither chalitzah nor yibum can be performed. While the reason for chalitzah is derived from a verse stating the man must be an adult, the reason for yibum is not explicitly stated. Rabbi Meir explains that for yibum, there is a concern that the minor male might grow up to be infertile (a saris) or the minor female might grow up to be barren (an ailoni), which are minority possibilities. In such a scenario, the yibum would be invalid, and the marriage would be forbidden as an incestuous union. The rabbis, however, question Rabbi Meir's stance on yibum, arguing that one should follow the majority, which is that minors will mature normally. This case highlights the difference between following the majority and being concerned for a minority.
Returning to the issue of tinuf (miscarriage), the Gemara clarifies the dispute between Rabbi Yishmael and Rabbi Yehoshua. Rabbi Yishmael maintains that tinuf does not exempt the animal from the firstborn status, meaning even if a miscarriage occurred, the next offspring is still a firstborn. Rabbi Yehoshua, however, holds that tinuf does exempt. The Gemara refines this: if tinuf is observed, it certainly exempts. The real question is whether we must be concerned that tinuf occurred even if not observed. Rabbi Yishmael would follow the majority that animals do not miscarry, thus making the offspring a vadai firstborn. Rabbi Yehoshua, being concerned for the minority that do miscarry, would consider it a safek.
The Gemara then points out an apparent contradiction: earlier, Rabbi Yishmael was presented as being concerned for a minority (regarding the age of maturity), but here he is said to follow the majority (regarding tinuf). The resolution is that Rabbi Yishmael is only concerned for a minority when it leads to a stringency (chumra), but not when it leads to a leniency (kula). In the case of the animal's age, being concerned for the minority that do not give birth within the first year leads to a safek firstborn, which is a stringency (as it requires waiting for a blemish). In the case of tinuf, being concerned for the minority that miscarry would lead to a leniency (exempting the offspring from firstborn status). Therefore, Rabbi Yishmael follows the majority that animals do not miscarry, making the offspring a vadai firstborn, which is a stringency.
An alternative explanation for the dispute between Rabbi Yishmael and Rabbi Yehoshua regarding tinuf is offered. This explanation suggests that Rabbi Yishmael is consistently concerned for a minority, whether it leads to a stringency or a leniency. The disagreement then centers on whether an animal that miscarries can still give birth within the same year. Rabbi Yishmael holds that if an animal had a miscarriage, it cannot give birth again within the same year. Therefore, if an animal gives birth within its first year, it must not have had a miscarriage earlier in that year, making the offspring a vadai firstborn. Rabbi Yehoshua, however, believes that an animal can miscarry and still give birth within the same year, thus making the offspring a safek.
The discussion then moves to a third opinion, that of Rabbi Yeshua (distinct from Rabbi Yehoshua), who presents his own tradition. He states that a goat that miscarries at six months can still give birth within its first year. Similarly, a sheep that miscarries in its first year can give birth within its second year. The Gemara seeks to understand the novelty of this statement compared to his earlier argument. The distinction lies in whether we follow the opinion of Zayidi, who holds that after a miscarriage, an animal cannot become pregnant for at least 30 days. According to Zayidi, if a goat miscarries at the end of six months, it cannot get pregnant until the eighth month. Since gestation takes five months, it would not be able to give birth within its first year. Therefore, if an animal is observed to give birth within its first year, it proves that the earlier observed "miscarriage" was not a true tinuf. Rabbi Yeshua, in his own opinion, does not follow Zayidi's rule, asserting that an animal can become pregnant immediately after a miscarriage. Thus, even if it miscarried at six months, it could still give birth within the first year, making the offspring a safek.
Another approach to explaining the difference between Rabbi Yeshua's tradition and his own opinion focuses on whether gestation must be a full five months or if a shorter period is acceptable. According to Rabbi Yeshua's tradition, gestation must be a full five months. Combined with Zayidi's 30-day rule post-miscarriage, this would mean a miscarriage at six months would prevent a birth within the first year. Therefore, a birth within the first year would indicate no true miscarriage. However, Rabbi Yeshua's own opinion is that gestation can be "shortened" (l'mekutain), meaning less than a full five months. In this case, even with Zayidi's 30-day rule, a miscarriage at six months could still allow for a birth within the first year, making the offspring a safek.
A third answer suggests that everyone agrees on Zayidi's 30-day rule and the full five-month gestation period. The dispute then hinges on whether a partial day counts as a full day (miktsat yom k'kulo) for calculating the gestation period. If a partial day counts as a full day, then conception on the first day of the eighth month could lead to birth by the end of the twelfth month, allowing for a birth within the first year despite a miscarriage at six months. If a partial day does not count, then the gestation period would extend into the next year, meaning a birth within the first year would preclude a prior miscarriage.
Finally, the Gemara returns to the opinion of Rabbi Akiva, who offers a simple rule: if it is certain there was no firstborn, the Kohen does not receive it. If it is certain there was a firstborn, the Kohen receives it. If it is a safek, the animal is blemished, and the owners may eat it. The Gemara then asks what distinguishes Rabbi Akiva's rule from Rabbi Yehoshua's. The distinction lies in the halachic significance of an animal producing milk. Rabbi Akiva holds that if an animal gives milk, it is a clear indication that it has given birth before, as the majority of animals only produce milk after giving birth. Therefore, if milk is observed, the offspring is definitively not a firstborn. Rabbi Yehoshua, however, is concerned for the minority of animals that produce milk without having given birth. Thus, for Rabbi Yehoshua, the presence of milk would still leave the offspring in a state of safek regarding its firstborn status.
This leads to an apparent contradiction with Rabbi Yehoshua's stance in the case of yibum, where he did not express concern for a minority. The Gemara resolves this by suggesting that the positions of Rabbi Akiva and Rabbi Yehoshua regarding milk should be reversed. Thus, Rabbi Yehoshua would follow the majority, concluding that milk indicates a prior birth and the offspring is not a firstborn. Rabbi Akiva, on the other hand, would be concerned for the minority that give milk without having given birth, making the offspring a safek. This interpretation ensures consistency in Rabbi Yehoshua's approach of not being concerned for a minority when it leads to a leniency, as in the case of yibum and here with milk, where following the majority leads to a leniency.