Numbers 3:4

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.

Numbers 3:4 In-Context

2 These are the names of the sons of Aaron: Nadab the first-born, and Abi'hu, Elea'zar, and Ith'amar;
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.
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.
Revised Standard Version of the Bible, copyright 1952 [2nd edition, 1971] by the Division of Christian Education of the National Council of the Churches of Christ in the United States of America. Used by permission. All rights reserved.