Numbers 1:2-5

²Take the sum of the whole assembly of the children of Israel, after their families, according to their fathers' houses, by the number of the names, every male, according to their polls;

³from twenty years and upward, all that go forth to military service in Israel: ye shall number them according to their hosts, thou and Aaron.

⁴And with you there shall be a man for every tribe, a man who is the head of his father's house.

⁵And these are the names of the men that shall stand with you: for Reuben, Elizur the son of Shedeur;