Matthew Poole and continuators on Joshua 22:21

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 ,

Either First properly, each was a Governour of a thousand: for there were among them divers Rulers, some of Tens, some of Hundreds, and some of Thousands; or rather, Secondly, improperly, and indefinitely, i. e. of the People of Israel, which consist of so many Thousands more than you, whose Authority therefore you owe a reverence to. For by comparing v. 14. these seem to be greater Persons than those that were Rulers of thousands.