Leviticus 16:7-10

16:7 He must then take the two goats and stand them before the Lord at the entrance of the Meeting Tent, 16:8 and Aaron is to cast lots over the two goats, one lot for the Lord and one lot for Azazel. 16:9 Aaron must then present the goat which has been designated by lot for the Lord, and he is to make it a sin offering, 16:10 but the goat which has been designated by lot for Azazel is to be stood alive before the Lord to make atonement on it by sending it away to Azazel into the wilderness.