Getting back to yesterday’s post, the Ba’al haMaor suggested that the machlokes between Rabbi Meir and Chachamim whether bi’ur chamietz (except the minimum necessary for seudas Shabbos) on Erev Pesach which falls on Shabbos must be done before Shabbos or can be done on Shabbos depends on the machlokes R’ Yehudah and Chachamim as to how bi’ur must be done. If bi’ur must be done by burning (R’ Yehudah’s opinion), then it must be done before Shabbos; if bi’ur can be done through any means of disposal, then it can be done even on Shabbos (as the Chachamim hold). The Rambam clearly disagrees with this analysis. Rambam paskens that bi’ur can be done by any means of disposal, but holds that bi’ur must be done before Shabbos. Why according to the Rambam can bi’ur not be done on Shabbos itself?
R’ Soloveitchik explained the Rambam based on a chiddush of Rashi in Beitzah (27b). Kodshim which are tamei, including challah or terumah which became tamei, are disposed of by burning. The Mishna in Shabbos (23) tells us that these items may not be burned on Shabbos or Yom Tov. Rashi writes that one should not interpret this gezeira narrowly as applying only to burning, but it includes any means of disposal, e.g. one would not be allowed to feed challah tamei'ah to one’s dog. Even though it seems no melacha is being done by feeding a dog challah temei’ah on Shabbos, Rashi writes that “rachmana achshivei l’havarasan” – the Torah declared disposal of kodshim to be a significant act and labeled it a melacha.
Using Rashi’s chiddush, R’ Soloveitchik argued that the same idea of “achshivei” applies to bi’ur chameitz as well as bi’ur kodshim. Any means of disposal of chameitz is prohibited on Shabbos. A footnote in the sefer Mo’addei haRav notes that R’ Soloveitchik would not dispose of his leftover chameitz crumbs by flushing them down the toilet on Shabbos in consideration on this view of the Rambam. (No other poskim to my knowledge share this view.) Instead, R' Soloveitchik relied on bittul alone.
R’ Soloveitchik’s equation of bi’ur chameitz and bi’ur kodshim is a major chiddush which flies in the face of a tshuvah of the Noda b’Yehudah (O.C. 15). Hopefully more on that to come…. As we get closer to Pesach there is less and less time to think and write, so posting is a bit difficult.