וְקָרַבְתָּ֗ מ֚וּל בְּנֵ֣י עַמּ֔וֹן אַל־תְּצֻרֵ֖ם וְאַל־תִּתְגָּ֣ר בָּ֑ם כִּ֣י לֹֽא־אֶ֠תֵּן מֵאֶ֨רֶץ בְּנֵי־עַמּ֤וֹן לְךָ֙ יְרֻשָּׁ֔ה כִּ֥י לִבְנֵי־ל֖וֹט נְתַתִּ֥יהָ יְרֻשָּֽׁה׃
e quando ti avvicini ai figli di Ammon, non molestarli e non contenderli; poiché non ti darò possesso del paese dei figli di Ammon; perché l'ho dato ai figli di Lot per un possesso.—
Rashbam on Deuteronomy
כי לבני לוט, on account of his having been Avraham’s nephew.
Chizkuni
וקרבת מול בני עמון, “when you come near to being opposite the Bney Ammon;” actually they did not get to the boundary of the Bney Ammon, as their lands were to the east of both the kingdoms of Sichon and Og, king of Bashan.