And their coast was Jazer, and all the cities of Gilead, and half the land of the children of Ammon, unto Aroer that is before Rabbah; Half the land on the children of Ammon - This probably was land which had been taken from the Ammonites by Sihon, king of the Amorites, and which the Israelites possessed by right of conquest. For although the Israelites were forbidden to take the land of the Ammonites, Deuteronomy 2:37, yet this part, as having been united to the territories of Sihon, they might possess when they defeated that king and subdued his kingdom.
Related Commentaries of Joshua 13:25
Joshua 13:25
25 And their coast was Jazer, and all the cities of Gilead, and half the land of the children of Ammon, unto Aroer that is before Rabbah;