Numbers 8:15-17

New Revised Standard Version, Anglicised Catholic Edition

¹⁵ Thereafter the Levites may go in to perform service at the tent of meeting, once you have cleansed them and presented them as an elevation-offering. 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,