Charles Ellicott Commentary Deuteronomy 2:19

"and when thou comest nigh over against the children of Ammon, vex them not, nor contend with them; for I will not give thee of the land of the children of Ammon for a possession; because I have given it unto the children of Lot for a possession." — Deuteronomy 2:19 (ASV)

And when thou comest nigh. —Compare Note on Deuteronomy 2:9.