Numbers 8:8-12

8Then let them take a young bull with its meat offering, even fine flour mixed with oil, and another young bull shalt thou take for a sin offering. 9And thou shalt bring the Levites before the tabernacle of the congregation: and thou shalt gather the whole assembly of the children of Israel together: 10And thou shalt bring the Levites before the LORD: and the children of Israel shall put their hands upon the Levites: 11And Aaron shall offer the Levites before the LORD for an offering of the children of Israel, that they may execute the service of the LORD.123 12And the Levites shall lay their hands upon the heads of the bulls: and thou shalt offer the one for a sin offering, and the other for a burnt offering, to the LORD, to make an atonement for the Levites.