Numbers 8:18-20

New Catholic Bible

¹⁸ But I have taken the Levites as a substitute for all the firstborn of the people of Israel. ¹⁹ I have given the Levites as a gift to Aaron and his sons from among the people of Israel, to perform the work of the people of Israel in the tent of meeting and to make atonement for the people of Israel, so that no plague may come upon the people of Israel when the people of Israel approach near the sanctuary.”

²⁰ So Moses and Aaron and all the assembly of the people of Israel did to the Levites what God had commanded Moses concerning the Levites, that is what the people of Israel did to them.