Numbers 3:4

4 Nadab and Abihu, however, died before the LORD when they made an offering with unauthorized fire before him in the Desert of Sinai. They had no sons, so Eleazar and Ithamar served as priests during the lifetime of their father Aaron.

Read Numbers 3:4 Using Other Translations

And Nadab and Abihu died before the LORD, when they offered strange fire before the LORD, in the wilderness of Sinai, and they had no children: and Eleazar and Ithamar ministered in the priest's office in the sight of Aaron their father.
But Nadab and Abihu died before the LORD when they offered unauthorized fire before the LORD in the wilderness of Sinai, and they had no children. So Eleazar and Ithamar served as priests in the lifetime of Aaron their father.
But Nadab and Abihu died in the LORD ’s presence in the wilderness of Sinai when they burned before the LORD the wrong kind of fire, different than he had commanded. Since they had no sons, this left only Eleazar and Ithamar to serve as priests with their father, Aaron.