Numbers 8:11 KJV

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.

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, unto the LORD, to make an atonement for the Levites.

13And thou shalt set the Levites before Aaron, and before his sons, and offer them for an offering unto the LORD.