Numbers 8:11-15

11Aaron is to present the Levites before the Lord as a presentation offering from the Israelites, so that they may perform the Lord’s work.

12Next the Levites are to lay their hands on the heads of the bulls. Sacrifice one as a sin offering and the other as a burnt offering to the Lord, to make atonement for the Levites.

13“You are to have the Levites stand before Aaron and his sons, and you are to present them before the Lord as a presentation offering.

14In this way you are to separate the Levites from the rest of the Israelites so that the Levites will belong to me.

15After that the Levites may come to serve at the tent of meeting, once you have ceremonially cleansed them and presented them as a presentation offering.