Numbers 21:24

Possessed his land from Arnon unto Jabbok, even unto the children of Ammon— This is a brief description of the extent of Sihon's country, which reached from the river Arnon, the bound of the Moabites country on the south, ch. Numbers 22:36 unto the river Jabbok, which was the bound of the Ammonites country on the north, Deuteronomy 3:16. Joshua 12:2; Joshua 13:10. For the border of the children of Ammon was strong; Houbigant renders, for the borders, &c. were fortified; and this is mentioned as one reason why the children of Israel did not attack their country. We are farther told, that they were forbidden to meddle with them, because they were the descendants of Lot, Deuteronomy 2:19. The border of the children of Ammon was rendered naturally strong by a ridge of mountains, which parted them from the kingdom of Sihon.