Deuteronomy 2:19

And when thou comest nigh over against the children of Ammon,.... Who dwelt near the Moabites, and were brethren, both descending from Lot, Genesis 19:37

distress them not, nor meddle with them: lay no siege to any of their cities, nor provoke them to war, nor engage in battle with them:

for I will not give thee of the land of the children of Ammon any possession; that is, any part of it which was now in their hands; otherwise half their land was given to the tribe of Gad; but then that was what Sihon king of the Amorites had taken from them, and which Israel retook from him, and so possessed it not as the land of the Ammonites, but of the Amorites, one of the seven nations, whose land they were to inherit; see Joshua 13:25,

because I have given it unto the children of Lot for a possession; the Ammonites were the children of Lot by his second daughter, Genesis 19:38.