Numbers 8:10-14

10When you bring the Levites before the Lord, the people of Israel shall lay their hands on the Levites,

11and Aaron shall offer the Levites before the Lord as a wave offering from the people of Israel, that they may do the service of the Lord.

12Then the Levites shall lay their hands on the heads of the bulls, and you shall offer the one for a sin offering and the other for a burnt offering to the Lord to make atonement for the Levites.

13And you shall set the Levites before Aaron and his sons, and shall offer them as a wave offering to the Lord.

14"Thus you shall separate the Levites from among the people of Israel, and the Levites shall be mine.