Only to the land of the sons of Ammon you did not draw near, that is, to all the banks of the river Jabbok and the cities of the hill country, whatever the LORD our God had forbidden us.
God having tried the self-denial of his people in forbidding them to meddle with the Moabites and Ammonites, and they having quietly passed by those rich countries, and, though superior in number, not made any attack upon them, here he recompenses them for their obedience by giving them possession of the country of Sihon king of the Amorites.
Commenting on Deuteronomy 2:24-37
Only unto the land of the children of Ammon thou camest not,.... Which was then in their possession; otherwise what Sihon had took away from them, that the children of Israel came into and enjoyed, as before observed, Deu 2:19.
Deu 2:37 Only along the land of the Ammonites the Israelites did not come, namely, along the whole of the side of the brook Jabbok, or the country of the Ammonites, which was situated upon the eastern side of the upper Jabbok, and the towns of the mountain, i.e., of the Ammonitish highlands, and “to all that the Lord had commanded,” sc., commanded them not to remove.