Leviticus 16:15-17

15“He shall then slaughter the goat for the sin offering for the people and take its blood behind the curtain and do with it as he did with the bull’s blood: He shall sprinkle it on the atonement cover and in front of it.

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.