The Torah says about the Korban Pesach sacrifice, which was offered on the 14th of Nissan, “Lo Tochal Alav Hametz” (Debarim 16:3) – “Do not eat leaven in conjunction with it.” This verse introduces a prohibition against eating Hametz throughout the time when the Korban Pesach may be offered, meaning, during the afternoon of the 14th of Nissan, Ereb Pesach. The Biblical prohibition takes effect at midday, which is the time when the Korban Pesach could be offered, but the Sages enacted a safeguard, forbidding Hametz already during the sixth hour.
The Sefer Ha’hinuch explains that the Torah introduced this prohibition due to the unique severity of the prohibition against eating Hametz during Pesach. This prohibition is treated with special stringency, the Sefer Ha’hinuch explains, because it commemorates the event of the Exodus – when Beneh Yisrael left hastily, and their dough did not have time to rise. The miracle of the Exodus is especially important as it confirms the belief that G-d created the universe and exerts absolute control over the world, and so all Misvot associated with the commemoration of this event is treated very stringently. Accordingly, the Sefer Ha’hinuch explains, the Torah made a safeguard for its own prohibition, forbidding the consumption of Hametz already during the afternoon of Ereb Pesach, before the onset of the Yom Tob. Due to the especially stringent nature of the Hametz prohibition, the Torah added a safeguard, extending the prohibition by six hours, such that we must refrain from Hametz already at midday on Ereb Pesach.
In addition to the prohibition against eating Hametz on the afternoon of Ereb Pesach, which the Torah commands in this verse (“Lo Tochal”), the Torah also forbids owning Hametz during this time. This law is derived from a different verse: “Ach Ba’yom Ha’rishon Tashbitu Se’or Mi’batechem” – “But on the first day, you shall eliminate leaven from your home” (Shemot 12:15). While we might initially assume that this refers to the first day of Pesach, in truth, it cannot refer to this day, because the Torah already forbids having Hametz in one’s possession throughout the seven days of Pesach. Therefore, the Sages understood that the word “Rishon” (“first”) refers to the day before Pesach, as this word can sometimes mean “preceding.” The implication of this command is that one may have Hametz in his possession during part of the day of Ereb Pesach, and then at some point one must eliminate all Hametz. The Torah does not specify when during this day one is required to eliminate Hametz from his possession. Quite reasonably, the Sefer Ha’hinuch writes, the Sages understood that half the day one is allowed to have Hametz, and during the second half this is prohibited. Thus, this verse establishes the prohibition against having Hametz in one’s possession during the afternoon of Ereb Pesach.
The Sefer Ha’hinuch notes that there were those who understood differently, claiming that the Sages inferred this Halacha from the word “Ach” (“But,” or “Only”) at the beginning of this phrase. There is a system of letter substitution called “Ahas Bata,” according to which the letter “Alef” is substituted with a “Het,” and “Chaf” is substituted with “Sadi,” such that “Ach” may be read as “Hetz,” which means “split in half.” These unnamed Rabbis thought that this is how the Sages derived from this verse the requirement to eliminate Hametz from one’s possession in the middle of the day on Ereb Pesach. The Sefer Ha’hinuch strongly denounces this far-fetched explanation, saying that those who advanced such a theory did not properly understand the words of Hazal.
This prohibition is binding upon both men and women, and applies in all places and in all time periods. One who eats a Ke’zayit of Hametz after midday on Ereb Pesach is in violation of this command and thus liable to Malkut.
The Sefer Ha’hinuch notes that his discussion follows the view of the Rambam, but the Ramban disagrees, and understands the command “Lo Tochal Alav Hametz” differently. In his view, there is only an affirmative command to eliminate Hametz from one’s possession at midday of Ereb Pesach, but one who eats Hametz on the afternoon of Ereb Pesach is not liable to Malkut. The Sefer Ha’hinuch concludes by emphasizing that different scholars have different understandings of Torah law, and “Elu Ve’elu Dibreh Elokim Haim” – they are all the words of Hashem’s Torah and worthy of our study and analysis.