Numbers 8:20-22 New American Bible (Revised Edition) (NABRE)
20 This, then, is what Moses and Aaron and the whole community of the Israelites did with respect to the Levites; the Israelites did exactly as the Lord had commanded Moses concerning them. 21 When the Levites had purified themselves[a] and washed their garments, Aaron presented them as an elevated offering before the Lord, and made atonement for them to cleanse them. 22 Only then did they enter upon their service in the tent of meeting under the supervision of Aaron and his sons. Exactly as the Lord had commanded Moses concerning the Levites, so it was done with regard to them.