Numbers 8:10-14

10and present the Levites before the Lord; and the sons of Israel 1shall lay their hands on the Levites. 11Aaron then shall 2present the Levites before the Lord as a 3wave offering from the sons of Israel, that they may 4qualify to perform the service of the Lord. 12Now 5the Levites shall lay their hands on the heads of the bulls; then offer the one for a sin offering and the other for a burnt offering to the Lord, to make atonement for the Levites. 13You shall have the Levites stand before Aaron and before his sons so as to present them as a wave offering to the Lord.

14“Thus you shall separate the Levites from among the sons of Israel, and 6the Levites shall be Mine.