Sicha, 11 Nissan & Acharon Shel Pesach 5737,
And Sicha. Shabbos Parshas Maasei 5742
A. How Could It Be Forgotten?
In the second year after the Exodus from Egypt, the Jews were commanded to bring the Pesach offering (Source 1). The Talmud tells us that the law regarding whether the Pesach offering overrides Shabbat was forgotten by the Sons of Beteira, until Hillel the Babylonian reminded them of the law (Source 2).
(The arguments for and against the Pesach offering overriding Shabbat: Since the Pesach offering is brought as a group offering, it has the characteristics of a communal sacrifice, and thus should override Shabbat like the daily tamid offering. On the other hand, since it is paid for by individuals and eaten only by those registered for it, it is not truly a communal sacrifice and should not override Shabbat.)
This raises a fundamental question: How could such a law be forgotten? It’s impossible for 14 years to pass without the day before Pesach falling on Shabbat (Source 3). Moreover, the Pesach offering was offered publicly and with great fanfare—even non-Jews wrote about it (Source 4)—so how could such a well-known law be lost?
The Tzlach explains: Until that year, they arranged the calendar so that the day before Pesach would not fall on Shabbat—similar to the rule of “Lo ADU Rosh” (Source 5). That year, however, they didn’t make the adjustment. This is what it means when it says “the law was forgotten.”
But the Rebbe rejects this explanation: We have no source that indicates that there was ever a longstanding custom to set the calendar to avoid Erev Pesach (the eve of Pesach) falling on Shabbat. Moreover, the second Pesach offering in the desert, and the first one after entering the Land of Israel, both occurred on Shabbat!
B. How Do Halachic Disputes Arise in Mitzvah Practice?
A similar question arises regarding disagreements over mitzvot that have been practiced continuously. For example: How many threads are to be twisted in a tzitzit string—three or four? (Source 6). Or the famous disagreement between Rashi and Rabbeinu Tam about the order of the passages in tefillin.
Jews have worn tefillin and tzitzit since the time of Moses. So how could such fundamental differences arise?
C. Diversity of Opinion in Judaism
There were many halachic disputes between Beit Shammai and Beit Hillel. For many years, each community followed the rulings of its own teachers. Yet Beit Shammai and Beit Hillel did not stop intermarrying.
Furthermore, the Talmud in various places says that the accepted halachah follows the local rabbi (Sources 7–8). However, once there was a formal vote and decision—nimnu vegamru—then the halachah was binding, and everyone was obligated to follow that decision.
So too in our case: It is likely that throughout the generations there was a dispute as to whether the Pesach offering overrides Shabbat. Some practiced one way, others the opposite.
So what did the Sons of Beteira forget? They forgot whether there had been a formal rabbinic vote and consensus that established the halachah. When Hillel arrived, he expressed his view—that the Pesach offering does override Shabbat—and the practice followed his opinion.
This same concept applies to the dispute between Rashi and Rabbeinu Tam regarding the tefillin passages. Both traditions existed simultaneously throughout the generations, and no definitive halachic ruling was made in favor of either one. In fact, archaeological findings of tefillin from the Second Temple era show that even then, Jews followed both customs.
