TSK · Numbers 26:61

Nadab and Abihu, the sons of Aaron, each took his censer, and put fire in it, and laid incense on it, and offered strange fire before Yahweh, which he had not commanded them.

Nadab and Abihu died before Yahweh, when they offered strange fire before Yahweh, in the wilderness of Sinai, and they had no children. Eleazar and Ithamar ministered in the priest's office in the presence of Aaron their father.