Leviticus 16:16-18

16In this way he will make atonement for the Most Holy Place because of the uncleanness and rebellion of the Israelites, whatever their sins have been. He is to do the same for the tent of meeting, which is among them in the midst of their uncleanness.

17No one is to be in the tent of meeting from the time Aaron goes in to make atonement in the Most Holy Place until he comes out, having made atonement for himself, his household and the whole community of Israel.

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