Adam Clarke on Joshua 14:1

Eleazar the priest, etc. - Eleazar, as being the minister of God in sacred things is mentioned first. Joshua, as having the supreme command in all things civil, is mentioned next. And the Heads or Princes of the twelve tribes, who in all things acted under Joshua, are mentioned last. These heads or princes were twelve, Joshua and Eleazar included; and the reader may find their names in Num 34:19-28. It is worthy of remark that no prince was taken from the tribes of Reuben and Gad, because these had already received their inheritance on the other side of Jordan, and therefore could not be interested in this division.