Leviticus 4:7-8

7And the priest shall put some of the blood on the horns of the altar of sweet incense before the Lord, which is in the tabernacle of meeting; and he shall pour the remaining blood of the bull at the base of the altar of the burnt offering, which is at the door of the tabernacle of meeting.

8He shall take from it all the fat of the bull as the sin offering. The fat that covers the entrails and all the fat which is on the entrails,