Numbers 3:3-5

Revised Standard Version Catholic Edition

³ these are the names of the sons of Aaron, the anointed priests, whom he ordained to minister in the priest’s office. ⁴ But Nadab and Abi′hu died before the Lord when they offered unholy fire before the Lord in the wilderness of Sinai; and they had no children. So Elea′zar and Ith′amar served as priests in the lifetime of Aaron their father.

The Duties of the Levites

⁵ And the Lord said to Moses,