Numbers 3:10-12

New Revised Standard Version, Anglicised Catholic Edition

¹⁰ But you shall make a register of Aaron and his descendants; it is they who shall attend to the priesthood, and any outsider who comes near shall be put to death.

¹¹ Then the Lord spoke to Moses, saying: ¹² I hereby accept the Levites from among the Israelites as substitutes for all the firstborn that open the womb among the Israelites. The Levites shall be mine,