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:

Concerning them Moses commanded. The arrangement itself, as well as the express terms on which he assented to it, was announced by the leader to the public authorities - i:e., the pastoral country the two tribes had desired was to be granted them on condition of their lending their aid to their brethren in the approaching invasion of Canaan. If they refused, or failed to perform their promise, those possessions should be forfeited, and themselves compelled to go across the Jordan, and fight for a settlement like the rest of their brethren.