John Wesley on Jeremiah 49:1

No heir - During the long tract of time that there were wars between the Jews and Ammonites, the land of Gad and Reuben which lay beyond Jordan, fell into the hands of the Syrians, Moabites, and Ammonites. Hence it is that the prophet saith, Hath Israel no sons? God had given that country of Gilead to Manasseh, Reuben, and Gad; and as mens estates ought to descend to their heirs, so this land should have descended to their posterity, but the Ammonites had taken and possessed it.