Leviticus 22:26-30

Lev 22:26 And Yahveh spoke to Moses, and this is what he said,
Lev 22:27 “When an ox or sheep or goat is born, it will remain seven days with its mother, and from the eighth day on it will be acceptable as a fire offering to Yahveh.
Lev 22:28 But you will not kill an ox or a sheep and her young in one day.
Lev 22:29 And when you sacrifice a sacrifice of thanksgiving to Yahveh, you will sacrifice it so that you may be accepted.
Lev 22:30 It will be eaten on the same day; you will leave none of it until morning: I am Yahveh.

consecration, not cruelty

Calvin commented on this passage that taking an immature animal fresh from the womb to the altar was a sign of contempt toward God, and would make people grow accustomed to cruelty. Our religion is supposed to show respect to God, and foster good habits, not cruel ones. A religion that does harm does not reflect the holiness and fairness of our God.

LORD, give us the courage to change our ways, when we discover that they do not reflect your image.