Charles Ellicott Commentary Leviticus 7:15

"And the flesh of the sacrifice of his peace-offerings for thanksgiving shall be eaten on the day of his oblation; he shall not leave any of it until the morning." — Leviticus 7:15 (ASV)

And the flesh of the sacrifice.—That is, after the priest had the breast and the shoulder, the offerer, his family, and any poor guests were to eat completely the share of the victim belonging to him, along with the remaining loaves, before morning , which at the time of the Second Temple was limited to midnight. This limitation of time was designed both to encourage generosity to the poor and to impress upon those who partook of it that it was a sacrificial and sacred feast, so as to prevent it from being turned into unseemly conviviality.