John Gill Commentary Joshua 22:13

"And the children of Israel sent unto the children of Reuben, and to the children of Gad, and to the half-tribe of Manasseh, into the land of Gilead, Phinehas the son of Eleazar the priest," — Joshua 22:13 (ASV)

And the children of Israel
In the land of Canaan:

sent to the children of Reuben, and to the children of Gad, and to
the half tribe of Manasseh, to the land of Gilead; they were possessed of, and had now returned to and dwelt in; they sent an embassy to them there, to inquire into the truth of what they had heard, and the reason of it, before they went to war with them, or proclaimed it, or took any further steps towards it; and which they were obliged to do by the above law, when there was any suspicion of idolatry, and any good ground and reason for it, (Deuteronomy 13:14);

And at the head of this deputation was Phinehas the son of Eleazar the priest; a man zealous for the Lord of hosts, and his glory, of which there is an instance in (Numbers 25:7Numbers 25:11Numbers 25:13); and so a fit person to be employed in this affair, who would be faithful, bold, and zealous, as well as capable of giving advice and counsel to both parties, if needful.