Numbers 3:11-13

11The Lord spoke to Moses:

12“See, I have taken the Levites from the Israelites in place of every firstborn Israelite from the womb. The Levites belong to me,

13because every firstborn belongs to me. At the time I struck down every firstborn in the land of Egypt, I consecrated every firstborn in Israel to myself, both man and animal. They are mine; I am the Lord.”