The Gemara in Masekhet Pesachim (28b) cites the view of Rabbi Shimon that the Torah prohibition against eating chametz on Pesach applies only on Pesach itself. Although it is forbidden also to eat chametz on the afternoon of the Erev Pesach, and to eat after Pesach chametz that had been owned by a Jew on Pesach, these prohibitions were – according to Rabbi Shimon – enacted by the Sages, and do not apply on the level of Torah law. This is in contrast to Rabbi Yehuda, who maintained that even the chametz prohibitions on Erev Pesach and after Pesach apply on the level of Torah law.
Rabbi Shimon draws proof to his position from a verse in Sefer Devarim (16:3) which appears to link the consumption of matza and refraining from chametz: “Do not eat chametz with it [the pesach sacrifice]; for seven days you shall eat with it matzot…” The implication of this verse, Rabbi Shimon contends, is that the chametz prohibition applies only when the mitzva of eating matza applies. In his words: “At the time when one is commanded to go ahead and eat matza, he is commanded not to eat chametz; at the time when he is not commanded to go ahead and eat matza, he is not commanded to eat chametz.” Therefore, the Torah prohibition of chametz is limited to the seven days of Pesach, and the prohibitions that apply before and after were enacted by the Sages.
The Penei Yehoshua noted that Rabbi Shimon here speaks of the mitzva of eating matza as a seven-day obligation. As we have discussed over the last two days, the Gemara elsewhere (Pesachim 120a) establishes that the obligation to eat matza in truth applies only the first night of Pesach. Rabbi Shimon, however, clearly states that there is a mitzva to eat matza all seven days of Pesach. The Penei Yehoshua explains that Rabbi Shimon apparently felt that although there is no obligation to eat matza after the first night of Pesach, one fulfills a mitzva by doing so. Rabbi Shimon’s inference might then provide us with a Talmudic basis for the view famously attributed to the Vilna Gaon that one fulfills a mitzva by eating matza anytime throughout Pesach, even after the first night.
The Rishonim disagree as to the final halakhic conclusion regarding the point of debate between Rabbi Shimon and Rabbi Yehuda. All agree that Halakha follows Rabbi Shimon’s position vis-à-vis the status after Pesach of chametz that had been owned by a Jew during Pesach. Such chametz, according to all opinions, is forbidden only by force of Rabbinic enactment, in accordance with Rabbi Shimon’s ruling. However, when it comes to the prohibition against eating chametz on the afternoon of Erev Pesach, several Rishonim accept Rabbi Yehuda’s view, that this prohibition applies on the level of Torah law. These include the Rambam (Hilkhot Chametz U-matza 1:8) and the Rosh (Pesachim 2:8). By contrast, the Ba’al Ha-ma’or and Ba’al Ha-ittur (cited by the Rosh) disagree, and maintain that Halakha accepts Rabbi Shimon’s view in its entirety, such that even in the afternoon of Erev Pesach, eating chametz is permissible according to Torah law and forbidden only by force of Rabbinic enactment.
If so, then it stands to reason that the Ba’al Ha-ma’or and Ba’al Ha-ittur accept the premise that eating matza constitutes a mitzva throughout all seven days of Pesach. After all, as we have seen, Rabbi Shimon’s view is predicated on his inference that the Torah prohibition of chametz is linked to the mitzva of eating matza – an inference which rests on the assumption that eating matza fulfills a mitzva all seven days. Seemingly, then, the Rishonim who accept the entirety of Rabbi Shimon’s opinion must accept this premise.
Indeed, as we saw earlier this week, the Ba’al Ha-ma’or (Pesachim 26b in the Rif) strongly implies that eating matza on Pesach after the first night fulfills a mitzva. The Ba’al Ha-ma’or draws a comparison between eating matza after the first night of Pesach and eating in the sukka after the first night of Sukkot. Just as one is not obligated to eat in the sukka after the first night of Sukkot (unless he wishes to eat a meal), but fulfills a mitzva by doing so, similarly, the Ba’al Ha-ma’or indicates, one fulfills a mitzva by eating matza after the first night of Pesach, even though this is not obligatory. The Ba’al Ha-ma’or is consistent with his acceptance of Rabbi Shimon’s view, which appears to be rooted in the assumption that eating matza fulfills a mitzva throughout the seven days of Pesach.
(Based on an article by Rav Yechiel Michael Rothschild in Kol Ha-Torah, vol. 65)