Numbers 8:20-22

20So Moses and Aaron and all the Israelites did those things to the Levites. The Israelites did everything that the Lord had said to Moses about the Levites.

21The Levites, too, made themselves clean and they washed their clothes. And Aaron brought them in front of Lord as a special gift. Aaron also burnt sacrifices to make them clean.

22After that, the Levites went in to do their work in the Tent of Meeting. They helped Aaron and his sons. The Israelites did everything with the Levites that the Lord had said to Moses about them.