But as for the cities that stood still in their strength, Israel burned none of them, save Hazor only; that did Joshua burn. The cities that stood still in their strength - The word תלם tillam, which we translate their strength, and the margin, their heap, has been understood two ways.
1. As signifying those cities which had made peace with the Israelites, when conditions of peace were offered according to the command of the law; and consequently were not destroyed. Such as the cities of the Hivites; see Joshua 11:19.
2. The cities which were situated upon hills and mountains, which, when taken, might be retained with little difficulty. In this sense the place is understood by the Vulgate, as pointing out the cities quae erant in collibus et tumulis sitae, "which were situated on hills and eminences." As the cities of the plain might be easily attacked and carried, Joshua destroyed them; but as those on mountains, hills, or other eminences, might be retained with little trouble, prudence would dictate their preservation, as places of refuge in any insurrection of the people, or invasion of their adversaries. The passage in Jeremiah, Jeremiah 30:18, Jerusalem shall be builded on her own heap, תלה tillah, if understood as above, conveys an easy and clear sense: Jerusalem shall be re-established on her Own Hill.