John Gill's  Exposition of the Bible 

Joshua 22:21

Then the children of Reuben and the children of Gad and the half tribe of Manasseh answered, and said unto the heads of the thousands of Israel,

Then the children of Reuben, and the children of Gad, and the half tribe of Manasseh, answered,.... By some person whom they appointed to deliver the answer in their name:

and said unto the heads of the thousands of Israel; who were over those that were rulers of the thousands of Israel, persons of greater authority than they, being princes of the respective tribes to which they belonged.