Leviticus 16:5-9

5And he shall take of the congregation of the children of Israel two he-goats for a sin-offering, and one ram for a burnt-offering.

6And Aaron shall present the bullock of the sin-offering, which is for himself, and make atonement for himself, and for his house. 7And he shall take the two goats, and set them before Jehovah at the door of the tent of meeting. 8And Aaron shall cast lots upon the two goats; one lot for Jehovah, and the other lot for Azazel. 9And Aaron shall present the goat upon which the lot fell for Jehovah, and offer him for a sin-offering.