Numbers 8:6-14
6 “Take the Levites from among the other Israelites and make them ceremonially clean.
7 To purify them, do this: Sprinkle the water of cleansing on them; then have them shave their whole bodies and wash their clothes, and so purify themselves.
8 Have them take a young bull with its grain offering of fine flour mixed with oil; then you are to take a second young bull for a sin offering.
9 Bring the Levites to the front of the Tent of Meeting and assemble the whole Israelite community.
10 You are to bring the Levites before the Lord, and the Israelites are to lay their hands on them.
11 Aaron is to present the Levites before the Lord as a wave offering from the Israelites, so that they may be ready to do the work of the Lord.
12 “After the Levites lay their hands on the heads of the bulls, use the one for a sin offering to the Lord and the other for a burnt offering, to make atonement for the Levites.
13 Have the Levites stand in front of Aaron and his sons and then present them as a wave offering to the Lord.
14 In this way you are to set the Levites apart from the other Israelites, and the Levites will be mine.