Numbers 3:11-13, 40-41

GOD spoke to Moses: “I have taken the Levites from among the People of Israel as a stand-in for every Israelite mother’s firstborn son. The Levites belong to me. All the firstborn are mine—when I killed all the firstborn in Egypt, I consecrated for my own use every firstborn in Israel, whether human or animal. They belong to me. I am GOD.”

GOD spoke to Moses: “Count all the firstborn males of the People of Israel who are one month and older. List their names. Then set apart for me the Levites—remember, I am GOD—in place of all the firstborn among the People of Israel, also the livestock of the Levites in place of their livestock. I am GOD.”