Deuteronomy 3:18

18.And I commanded you at that time. This address is directed only to those to whom an inheritance was given on the other side of Jordan; but Moses declares that he had introduced an agreement that the two tribes and a half should not enjoy their possession until they had accommpanied their brethren in the subjugation of the land of Canaan. He says, therefore, that he had given them a place, not where they were at once to settle themselves, but where they might deposit their wives and cattle, until the whole people were peaceably established in their land.