Albert Barnes Commentary Deuteronomy 2:9

"And Jehovah said unto me, Vex not Moab, neither contend with them in battle; for I will not give thee of his land for a possession; because I have given Ar unto the children of Lot for a possession." — Deuteronomy 2:9 (ASV)

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.