Leviticus 16:31-34

³¹It is a special Sabbath for you, and you are to keep yourselves from pleasure; it is an order for ever.

³²And the man on whose head the holy oil has been put, and who has been marked out to be a priest in his father's place, will do what is necessary to take away sin, and will put on the linen clothing, even the holy robes:

³³And he will make the holy place and the Tent of meeting and the altar free from sin; he will take away sin from the priests and from all the people.

³⁴And let this be an order for ever for you, so that the sin of the children of Israel may be taken away once every year. And he did as the Lord gave orders to Moses.