The Bible
Leviticus 16
How and when Aaron must enter the holy place is explained—Sacrifices are offered to reconcile Israel to God—The scapegoat carries away the sins of the people—The sins of all Israel are forgiven on the Day of Atonement.
9And Aaron shall bring the goat upon which the Lord’s lot fell, and offer him for a sin offering.
25And the fat of the sin offering shall he burn upon the altar.
31It shall be a sabbath of rest unto you, and ye shall afflict your souls, by a statute for ever.