Leviticus 16:3-10

But in this way Aaron shall come into the Holy Place: with a bull from the herd for a sin offering and a ram for a burnt offering. He shall put on the holy linen coat and shall have the linen undergarment on his body, and he shall tie the linen sash around his waist, and wear the linen turban; these are the holy garments. He shall bathe his body in water and then put them on. And he shall take from the congregation of the people of Israel two male goats for a sin offering, and one ram for a burnt offering. “Aaron shall offer the bull as a sin offering for himself and shall make atonement for himself and for his house. Then he shall take the two goats and set them before the LORD at the entrance of the tent of meeting. And Aaron shall cast lots over the two goats, one lot for the LORD and the other lot for Azazel. And Aaron shall present the goat on which the lot fell for the LORD and use it as a sin offering, but the goat on which the lot fell for Azazel shall be presented alive before the LORD to make atonement over it, that it may be sent away into the wilderness to Azazel.