Leviticus 16:29-34

“This shall be a permanent statute for you: in the seventh month (nearly October) on the tenth day of the month you shall humble yourselves [by fasting] and not do any work, whether the native-born or the stranger who lives temporarily among you; for it is on this day that atonement shall be made for you, to cleanse you; you will be clean from all your sins before the LORD. [Heb 10:1, 2; 1 John 1:7, 9] It is a Sabbath of solemn rest for you, and you shall humble yourselves; it is a permanent statute. So the priest who is anointed and ordained to serve and minister as priest in his father’s place shall make atonement: he shall wear the holy linen garments, 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.