Numbers 8:19-21

Revised Standard Version

¹⁹ And I have given the Levites as a gift to Aaron and his sons from among the people of Israel, to do the service for the people of Israel at the tent of meeting, and to make atonement for the people of Israel, that there may be no plague among the people of Israel in case the people of Israel should come near the sanctuary.”

²⁰ Thus did Moses and Aaron and all the congregation of the people of Israel to the Levites; according to all that the Lord commanded Moses concerning the Levites, the people of Israel did to them. ²¹ And the Levites purified themselves from sin, and washed their clothes; and Aaron offered them as a wave offering before the Lord, and Aaron made atonement for them to cleanse them.