The Moabites and the Ammonites Deuteronomy 2:19 being descended from Lot, the nephew of Abraham Genesis 19:30-38, were, like the Edomites, kinsmen of the Israelites.
Matthew Henry
Concise Bible Commentary
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.
SDA Bible Commentary (limited)
Volume 1-7
9. Given Ar. The descendants of Lot, like those of Ishmael and Esau, had their inheritance confirmed to them before the seed of Abraham occupied what had been assigned to them. Ar was apparently the chief city of that territory, and gave its name to the entire region (Num. 21:15, 28).