Numbers 8:6-12

6“Take the Levites from among the children of Israel and cleanse them ceremonially.

7Thus you shall do to them to cleanse them: Sprinkle water of purification on them, and let them shave all their body, and let them wash their clothes, and so make themselves clean.

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

9And you shall bring the Levites before the tabernacle of meeting, and you shall gather together the whole congregation of the children of Israel.

10So you shall bring the Levites before the Lord, and the children of Israel shall lay their hands on the Levites;

11and Aaron shall offer the Levites before the Lord like a wave offering from the children of Israel, that they may perform the work of the Lord.

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