Leviticus 16:33

“Then Aaron shall bring near the bull of the sin offering, which is for himself, and make atonement for himself and for his household, and he shall slaughter the bull of the sin offering which is for himself.

‘Then on the tenth day of this seventh month you shall have a holy convocation, and you shall humble yourselves; you shall not do any work.

‘Thus says Lord Yahweh, “In the first month, on the first of the month, you shall take a bull from the herd without blemish and purify the sanctuary.

but into the second, only the high priest enters once a year, not without taking blood, which he offers for himself and for the sins of the people committed in ignorance.