Numbers 8:15-17

New Catholic Bible

¹⁵ After this the Levites can go in and serve the needs of the tent of meeting, when you have purified them and offered them as a wave offering. ¹⁶ They are to be wholly dedicated to me from among the people of Israel. I have reserved them for myself as a substitute for all those who open the womb, the firstborn of the people of Israel. ¹⁷ All the firstborn of the people of Israel belong to me, both human and animal. I sanctified them to myself on the day that I killed every firstborn in the land of Egypt.