Numbers 8:21 WEB

¹⁹  I have given the Levites as a gift to Aaron and to his sons from among the children of Israel, to do the service of the children of Israel in the Tent of Meeting, and to make atonement for the children of Israel; that there be no plague among the children of Israel, when the children of Israel come near to the sanctuary.'

²⁰  Thus did Moses, and Aaron, and all the congregation of the children of Israel, to the Levites. According to all that Yahweh commanded Moses concerning the Levites, so the children of Israel did to them.

²¹  The Levites purified themselves from sin, and they washed their clothes; and Aaron offered them for a wave offering before Yahweh; and Aaron made atonement for them to cleanse them.

²²  After that, the Levites went in to do their service in the Tent of Meeting before Aaron, and before his sons: as Yahweh had commanded Moses concerning the Levites, so they did to them.

²³  Yahweh spoke to Moses, saying,