Leviticus 16:33-34

and make atonement for the Holy Sanctuary, and he shall make atonement for the Tent of Meeting, and for the altar [of burnt offering in the court]. He shall also make atonement for the priests and for all the people of the assembly. This shall be a permanent statute for you, so that atonement may be made for the children of Israel for all their sins once a year.” So he did just as the LORD had commanded Moses.