Leviticus 16:16-18

16So he shall make atonement for the Most Holy Place because of the impurities and rebellious acts of the Israelites in regard to all their sins. He is to do the same for the Tent of Meeting which abides among them in the midst of their impurities. 17No one may be in the Tent of Meeting from the time Aaron goes in to make atonement in the Most Holy Place until he leaves, after he has made atonement for himself, his household, and the whole assembly of Israel.

18Then he shall go out to the altar that is before the LORD and make atonement for it. He is to take some of the bull’s blood and some of the goat’s blood and put it on all the horns of the altar.