Kommentar zu Schemot 12:10

והנתר ממנו עד בקר AND THAT WHICH REMAINETH OF IT UNTIL THE MORNING — What does Scripture intend to teach by stating עד בקר a second time? It intends to add an earlier stage of morning to the stage of morning already mentioned: because the term morning usually signifies the period beginning with sun-rise, and Scripture here intends to advance the hour and forbid eating it even from the break of day. This is the explanation according to what the text really implies. And there is still another Halacha derived from it: it teaches that it is not to be burnt on the festival itself but on the following day, and this is how you must explain it: “[and ye shall not leave anything of it until the morning]”; והנתר ממנו “and as regards that which is left of it” unto that first morning (עד בקר), until the second morning shalt thou wait, and then shalt thou burn it (Mekhilta d'Rabbi Yishmael 12:10; Pesachim 83b; Shabbat 24b).

Because “morning” signifies the time of sunrise. . . This is puzzling, for in many places in the Talmud we see that בקר refers to daybreak עמוד השחר , and Rashi clearly says so himself in Berachos 9a and Pesachim 120b. (Nachalas Yaakov)

(Exodus 12:10) "And you shall not leave over anything of it until the morning, and what is left over of it until the morning, in fire shall you burn it." What is the intent of (the seemingly redundant) "until the morning"? To set a bound for the morning of morning (i.e., that he may eat it (only) until the rising of the morning star, and not until sunrise). Variantly: What is the intent of "until morning"? To teach that it is not burned until the eve of the sixteenth (of Nissan). R. Yishmael says: This is not necessary, for it is written (Ibid. 16) "No labor shall be done in them" (the festival days), and burning is in the category of "labor." What, then, is the intent of "until morning"? If the eve of the sixteenth occurred on Shabbat, it is not burned until the seventeenth. R. Yonathan says: This is not necessary, if where all ochel nefesh overrides the festival — the burning of the left-overs of the Pesach does not override the festival, then, where partial ochel nefesh does not override the Sabbath, how much more so should the burning of the left-overs of the Pesach not override the Sabbath! What, then, is the intent of "until morning"? To set a bound for the morning or morning (see above). R. Yitzchak says: (A verse) is not necessary (to tell us that left-overs of the Pesach may not be burned on the festival). For if the burning of chametz, which is interdicted in being seen or being found, does not override the festival, how much more so should the burning of the left-overs of the Pesach not override the festival. What, then, is the intent of "until morning"? As stated above.