Leviticus 3:8-9

8lay his hand on the head of his offering, and kill it in front of the tent of meeting; and Aaron's sons shall throw its blood against the sides of the altar.

9Then from the sacrifice of the peace offering he shall offer as a food offering to the Lord its fat; he shall remove the whole fat tail, cut off close to the backbone, and the fat that covers the entrails and all the fat that is on the entrails