Leviticus 22:26-30

26And the Lord spoke to Moses, saying:

27“When a bull or a sheep or a goat is born, it shall be seven days with its mother; and from the eighth day and thereafter it shall be accepted as an offering made by fire to the Lord.

28Whether it is a cow or ewe, do not kill both her and her young on the same day.

29And when you offer a sacrifice of thanksgiving to the Lord, offer it of your own free will.

30On the same day it shall be eaten; you shall leave none of it until morning: I am the Lord.