Numbers 8:8-12

8Then let them take a young bull and its grain offering of fine flour mixed with oil, and you shall take another young bull as a sin offering.

9You shall present the Levites before the Tent of Meeting (tabernacle), and you shall also assemble the whole congregation of the children of Israel,

10and present the Levites before the Lord, and the Israelites shall lay their hands on the Levites.

11Aaron shall present the Levites before the Lord as a wave offering from the Israelites, so that they may perform the service of the Lord.

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