Numbers 8:16-18

Revised Standard Version Catholic Edition

¹⁶ For they are wholly given to me from among the people of Israel; instead of all that open the womb, the first-born of all the people of Israel, I have taken them for myself. ¹⁷ For all the first-born among the people of Israel are mine, both of man and of beast; on the day that I slew all the first-born in the land of Egypt I consecrated them for myself, ¹⁸ and I have taken the Levites instead of all the first-born among the people of Israel.