They set out from there and camped along the Arnon, which is in the wilderness extending into Amorite territory. The Arnon is also the border between Moab and the Amorites.
“‘Rise up, journey on, and cross over the Wadi Arnon. See, I have handed over Sihon the Amorite, king of Heshbon, and his land—begin to possess it! Engage him in battle!
traveled through the wilderness, around the land of Edom and the land of Moab, came to the east side of the land of Moab and they camped on the other side of the Arnon. But they did not enter the territory of Moab, for the Arnon was the border of Moab.