Rashi on Deuteronomy
ונפן ונעל AND WE TURNED AND WENT UP — every journey towards the north (from the wilderness towards Canaan) is “uphill”.
Rav Hirsch on Torah
Kap. 3. V. 1. ונפן. Abweichend von dem ammonitischen Gebiete. ׳ויצא וגו Daher ward ihm kein Friedensangebot gesandt (רמב׳׳ן).
Chizkuni
ונפן ונעל, “we turned around and ascended; from the south to the north.”