Leviticus 16:29-34

“This is standard practice for you, a perpetual ordinance. On the tenth day of the seventh month, both the citizen and the foreigner living with you are to enter into a solemn fast and refrain from all work, because on this day atonement will be made for you, to cleanse you. In the presence of GOD you will be made clean of all your sins. It is a Sabbath of all Sabbaths. You must fast. It is a perpetual ordinance. “The priest who is anointed and ordained to succeed his father is to make the atonement: He puts on the sacred linen garments; He purges the Holy of Holies by making atonement; He purges the Tent of Meeting and the Altar by making atonement; He makes atonement for the priests and all the congregation. “This is a perpetual ordinance for you: Once a year atonement is to be made for all the sins of the People of Israel.” And Aaron did it, just as GOD commanded Moses.