Numbers 8:16-18

New Revised Standard Version, Anglicised Catholic Edition

¹⁶ For they are unreservedly given to me from among the Israelites; I have taken them for myself, in place of all that open the womb, the firstborn of all the Israelites. ¹⁷ For all the firstborn among the Israelites are mine, both human and animal. On the day that I struck down all the firstborn in the land of Egypt I consecrated them for myself, ¹⁸ but I have taken the Levites in place of all the firstborn among the Israelites.