Numbers 3:4-6

Revised Standard Version

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, ⁶ “Bring the tribe of Levi near, and set them before Aaron the priest, that they may minister to him.