Shegagos on Two Toldos: The Rambam's Yeruli and Forms of the Same Av

The shiur opens with a detailed analysis of a Rambam (רמב"ם) in Hilchos Shegagos (7:4) that rules yeruli—seemingly without explicit Talmudic support—that one who performs toldos of two different avos b'helem echad is liable for two chataos. This ruling puzzles the commentators, particularly Rabbeinu Avrohom ben HaRambam, because the Gemara (גמרא) in Bava Kamma appears to address only the case of two toldos from the same av, not two toldos from different avos. Rabbi Zweig presents Rabbeinu Avrohom's fundamental approach to resolving this difficulty. Rabbeinu Avrohom suggests that the Gemara's discussion of "shnei avos" and "shnei toldos" does not refer to two entirely different principles (different avos melachos) but rather to two different forms of the same principle. When the Gemara says one is liable for "shnei avos," it means two manifestations of the same av—such as ofeh and mevashel (both forms of bishul), or notei'a and zorei'a (both forms of planting). Similarly, "shnei toldos" means two different toldos that are both derived from the same av but appear in different forms. The Gemara's havah amina was that different forms of the same principle obligate separately, and this was rejected. According to Rabbeinu Avrohom, the Gemara never actually discussed the case of two entirely separate principles (two different avos), and therefore the Rambam's ruling about two toldos from different avos remains yeruli—a novel statement not derived from this Gemara.