12 The Horites formerly dwelt in Seir, but the descendants of Esau dispossessed them and destroyed them from before them, and dwelt in their place, just as Israel did to the land of their possession which the Lord gave them.) 13 " 'Now rise and cross over the Valley of the Zered.' So we crossed over the Valley of the Zered. 14 And the time we took to come from Kadesh Barnea until we crossed over the Valley of the Zered was thirty-eight years, until all the generation of the men of war was consumed from the midst of the camp, just as the Lord had sworn to them. 15 For indeed the hand of the Lord was against them, to destroy them from the midst of the camp until they were consumed. 16 "So it was, when all the men of war had finally perished from among the people, 17 that the Lord spoke to me, saying: 18 'This day you are to cross over at Ar, the boundary of Moab. 19 And when you come near the people of Ammon, do not harass them or meddle with them, for I will not give you any of the land of the people of Ammon as a possession, because I have given it to the descendants of Lot as a possession.' " 20 (That was also regarded as a land of giants; giants formerly dwelt there. But the Ammonites call them Zamzummim, 21 a people as great and numerous and tall as the Anakim. But the Lord destroyed them before them, and they dispossessed them and dwelt in their place, 22 just as He had done for the descendants of Esau, who dwelt in Seir, when He destroyed the Horites from before them. They dispossessed them and dwelt in their place, even to this day.
Matthew Henry's Commentary on Deuteronomy 2:12-22
Commentary on Deuteronomy 2:8-23
(Read Deuteronomy 2:8-23)
We have the origin of the Moabites, Edomites, and Ammonites. Moses also gives an instance older than any of these; the Caphtorims drove the Avims out of their country. These revolutions show what uncertain things wordly possessions are. It was so of old, and ever will be so. Families decline, and from them estates are transferred to families that increase; so little continuance is there in these things. This is recorded to encourage the children of Israel. If the providence of God has done this for Moabites and Ammonites, much more would his promise do it for Israel, his peculiar people. Cautions are given not to meddle with Moabites and Ammonites. Even wicked men must not be wronged. God gives and preserves outward blessings to wicked men; these are not the best things, he has better in store for his own children.