Numbers 8:8-12

8And they shall take a young bullock and its oblation of fine flour mingled with oil; and another young bullock shalt thou take for a sin-offering.

9And thou shalt bring the Levites before the tent of meeting; and thou shalt gather together the whole assembly of the children of Israel.

10And thou shalt bring the Levites before Jehovah; and the children of Israel shall put their hands upon the Levites.

11And Aaron shall offer the Levites as a wave-offering before Jehovah from the children of Israel, and they shall perform the service of Jehovah.

12And the Levites shall lay their hands upon the heads of the bullocks, and thou shalt offer the one for a sin-offering, and the other for a burnt-offering, to Jehovah, to make atonement for the Levites.