Numbers 3:4-6

Young's Literal Translation

⁴ And Nadab dieth -- Abihu also -- before Jehovah, in their bringing near strange fire before Jehovah, in the wilderness of Sinai, and sons they had not; and Eleazar -- Ithamar also -- acteth as priest in the presence of Aaron their father.

⁵ And Jehovah speaketh unto Moses, saying,

⁶ `Bring near the tribe of Levi, and thou hast caused it to stand before Aaron the priest, and they have served him,