Numbers 8:18-20

New Revised Standard Version, Anglicised Catholic Edition

¹⁸ but I have taken the Levites in place of all the firstborn among the Israelites. 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.