Leviticus 16:15-16

“Then Aaron must slaughter the first goat as a sin offering for the people and carry its blood behind the inner curtain. There he will sprinkle the goat’s blood over the atonement cover and in front of it, just as he did with the bull’s blood. Through this process, he will purify the Most Holy Place, and he will do the same for the entire Tabernacle, because of the defiling sin and rebellion of the Israelites.