Numbers 8:11-15

11Aaron then shall 1present the Levites before the Lord as a 2wave offering from the sons of Israel, that they may 3qualify to perform the service of the Lord. 12Now 4the 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 5the Levites shall be Mine. 15Then after that the Levites may go in to serve the tent of meeting. But you shall cleanse them and 6present them as a wave offering;