Numbers 8:17-19

Complete Jewish Bible

¹⁷ For all the firstborn among the people of Isra’el are mine, both humans and animals; on the day I struck all the firstborn in the land of Egypt, I set them apart for myself. ¹⁸ But I have taken the L’vi’im in place of all the firstborn among the people of Isra’el, ¹⁹ and I have given the L’vi’im to Aharon and his sons from among the people of Isra’el to do the service of the people of Isra’el in the tent of meeting and to make atonement for the people of Isra’el, so that no plague will fall on the people of Isra’el in consequence of their coming too close to the sanctuary.”