Numbers 8:8-10

Amplified Bible

⁸ Then 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. ⁹ You shall present the Levites before the Tent of Meeting (tabernacle), and you shall also assemble the whole congregation of the children of Israel, ¹⁰ and present the Levites before the Lord, and the Israelites shall lay their hands on the Levites.