Numbers 1:2-5
1:2 “Take a census of the entire Israelite community by their clans and families, counting the name of every individual male.
1:3 You and Aaron are to number all in Israel who can serve in the army, those who are twenty years old or older, by their divisions.
1:4 And to help you there is to be a man from each tribe, each man the head of his family.
1:5 Now these are the names of the men who are to help you: from Reuben, Elizur son of Shedeur;