Numbers 10:18
And the standard of the camp of Reuben set forward according to their armies: and over his host was Elizur the son of Shedeur. And the standard of the camp of Reuben set forward according to their armies: and over his host was Elizur the son of Shedeur.
Israel moved through the wilderness not as a crowd but in a fixed arrangement, tribe by tribe in their appointed places. Each camp advanced under its own standard, keeping its distinct position in the line of march. In that order the camp of Reuben set forward according to its armies, with Elizur the son of Shedeur over its host.