Reference for Chagigah 34:4

צריכא דאי אשמעינן בהא בהא קא אמרי ב"ש משום דאפשר למחר אבל הכא אימא מודו להו לב"ה

We need this statement [that Beit Hillel and Beit Shammai disagree over whether there is a make-up slaughtering day], because if [the Mishnah] only taught us this [second statement regarding the permissibility of bringing certain offering on the festival, we would think that] in this case, the House of Shammai say [that you may not bring elevation offerings], because it is possible to bring them the next day; but here [in the case where the next day is Shabbat], they would agree with the House of Hillel.

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