Numbers 8:19-21

New Revised Standard Version, Anglicised Catholic Edition

¹⁹ Moreover, I have given the Levites as a gift to Aaron and his sons from among the Israelites, to do the service for the Israelites at the tent of meeting, and to make atonement for the Israelites, in order that there may be no plague among the Israelites for coming too close to the sanctuary.

²⁰ Moses and Aaron and the whole congregation of the Israelites did with the Levites accordingly; the Israelites did with the Levites just as the Lord had commanded Moses concerning them. ²¹ The Levites purified themselves from sin and washed their clothes; then Aaron presented them as an elevation-offering before the Lord, and Aaron made atonement for them to cleanse them.