Numbers 1:2-5

²Take ye the sum of all the congregation of the children of Israel, by their families, by their fathers’ houses, according to the number of the names, every male, by their polls;

³from twenty years old and upward, all that are able to go forth to war in Israel, thou and Aaron shall number them by their hosts.

⁴And with you there shall be a man of every tribe; every one head of his fathers’ house.

⁵And these are the names of the men that shall stand with you. Of Reuben: Elizur the son of Shedeur.