Numbers 3:39-41

New Revised Standard Version Catholic Edition

³⁹ The total enrollment of the Levites whom Moses and Aaron enrolled at the commandment of the Lord, by their clans, all the males from a month old and upward, was twenty-two thousand.

The Redemption of the Firstborn

⁴⁰ Then the Lord said to Moses: Enroll all the firstborn males of the Israelites, from a month old and upward, and count their names. ⁴¹ But you shall accept the Levites for me—I am the Lord—as substitutes for all the firstborn among the Israelites, and the livestock of the Levites as substitutes for all the firstborn among the livestock of the Israelites.