Numbers 8:16-18

American Standard Version

¹⁶ For they are wholly given unto me from among the children of Israel; instead of all that openeth the womb, even the first-born of all the children of Israel, have I taken them unto me. ¹⁷ For all the first-born among the children of Israel are mine, both man and beast: on the day that I smote all the first-born in the land of Egypt I sanctified them for myself. ¹⁸ And I have taken the Levites instead of all the first-born among the children of Israel.