Numbers 32:28
So concerning them Moses commanded Eleazar the priest, and Joshua the son of Nun, and the chief fathers of the tribes of the children of Israel: So concerning them Moses commanded Eleazar the priest, and Joshua the son of Nun, and the chief fathers of the tribes of the children of Israel:
Concerning the tribes of Gad and Reuben, Moses entrusted their agreement to Eleazar the priest, to Joshua the son of Nun, and to the chief fathers of the tribes of the children of Israel. By that charge he made those leaders witnesses of the compact and parties responsible for seeing it kept. The promise thus secured was that the two tribes would cross over and fight alongside their brethren until those brethren had received their inheritance. The arrangement therefore teaches that professed believers must not seek ease for themselves while others bear the burdens of God's cause, for all alike are responsible to share in its work.