Numbers 4:1-3

Young's Literal Translation

4 And Jehovah speaketh unto Moses, and unto Aaron, saying,

² `Take up the sum of the sons of Kohath from the midst of the sons of Levi, by their families, by the house of their fathers;

³ from a son of thirty years and upward, even till a son of fifty years, every one going in to the host, to do work in the tent of meeting.