Heshbon—the city of Sihon— Heshbon was the capital city of the Amorites, and their king's seat; and Sihon is thought to be the name common to all the kings of the Amorites, as Pharaoh was to the kings of Egypt: so that the meaning is, that one of the kings of the Amorites made an inroad into the Kingdom of the Moabites, and took from them Heshbon, &c. Moses here remarks, that when the Israelites conquered those lands, they were not in the possession of the Moabites, but of the Amorites; and, consequently, that their title to them was good, notwithstanding the prohibition (Deuteronomy 9:19.) against meddling with the lands of the Moabites and Ammonites.
This precaution appears to have been very necessary; for we find that a contest arose afterwards, on this very head, between the Israelites and the Ammonites, Judges 11:13. THE former king of Moab, should rather be rendered a former king of Moab; for it is not certain that it was that king of Moab who reigned immediately before Sihon.