Leviticus 16:2-6

and the LORD said to Moses: “Tell Aaron your brother not to come at just any time into the Holy Place inside the veil, before the mercy seat which is on the ark, lest he die; for I will appear in the cloud above the mercy seat. “Thus Aaron shall come into the Holy Place: with the blood of a young bull as a sin offering, and of a ram as a burnt offering. He shall put the holy linen tunic and the linen trousers on his body; he shall be girded with a linen sash, and with the linen turban he shall be attired. These are holy garments. Therefore he shall wash his body in water, and put them on. And he shall take from the congregation of the children of Israel two kids of the goats as a sin offering, and one ram as a burnt offering. “Aaron shall offer the bull as a sin offering, which is for himself, and make atonement for himself and for his house.