Numbers 3:4

4But Nadab and Abihu died in the presence of the Lord when they offered strange (unholy, unacceptable, inappropriate) fire before the Lord in the Wilderness of Sinai; and they had no sons. So Eleazar and Ithamar served as priests 3:4 Lit before the face.in the presence and under the supervision of Aaron their father. [Lev 10:1-4]