Numbers 8:8-12

8Then let them take a young bullock, and its meal-offering, fine flour mingled with oil; and another young bullock shalt thou take for a sin-offering. 9And thou shalt present the Levites before the tent of meeting: and thou shalt assemble the whole congregation of the children of Israel: 10and thou shalt present the Levites before Jehovah. And the children of Israel shall lay their hands upon the Levites: 11and Aaron shall offer the Levites before Jehovah for a wave-offering, on the behalf of the children of Israel, that it may be theirs to do the service of Jehovah. 12And the Levites shall lay their hands upon the heads of the bullocks: and offer thou the one for a sin-offering, and the other for a burnt-offering, unto Jehovah, to make atonement for the Levites.