Zevachim 87A

חצות שני עוכלתן, רב חסדא אמר: עמוד השחר עוכלתן.

The second midnight, i.e., midnight of the following night, renders them consumed, and if they were dislodged from the altar after that they are not returned. Rav Ḥisda says: Dawn following the first evening renders them consumed, and if they were dislodged from the altar after that they are not returned.

אמרי בי רב: מאי טעמא דרב חסדא? ומה חצות שאין עושה לינה, עושה עיכול; עמוד השחר שעושה לינה, אינו דין שעושה עיכול?

They say in the school of Rav: What is the reasoning of Rav Ḥisda, who says that dawn renders these limbs consumed? It is the following a fortiori inference: And if midnight, which does not cause the disqualification of being left overnight with regard to limbs that were left off the altar until that time, still causes consumption, i.e., limbs burned on the altar until midnight are considered entirely consumed, then certainly with regard to dawn, which causes the disqualification of being left overnight with regard to limbs that were not left off the altar until that time, isn’t it logical that it causes consumption?

פירשו קודם חצות, והחזירן לאחר עמוד השחר ⁠– רבה אמר: חצות שני עוכלתן, רב חסדא אמר: אין בהן עיכול לעולם.

These amora’im also dispute the halakha in a case where the limbs separated from the altar before midnight and were returned to the altar after dawn: Rabba says that the second midnight renders them consumed, and if they separated after this time they are not returned. Rav Ḥisda says: Since these limbs were not returned to the altar by dawn, they are never subject to consumption through the passage of time. Rather, they are returned to the altar and allowed to burn until they are reduced to ash. These two disputes between Rabba and Rav Ḥisda indicate that both agree that limbs not on the altar by midnight are not considered consumed.