After that, they crossed the gorge of the River Arnon and camped in the Moabite desert bordering Amorite territory. The Arnon was the border between the Moabites and the Amorites.
But Sihon refused to let Israel travel through his land. Instead, he called together his entire army and marched into the desert to attack Israel near the town of Jahaz.
The LORD told me, “Don't try to start a war with Moab. Leave them alone, because I gave the land of Ar to them, and I will not let you have any of it.”
A little later, the Israelites set out into the desert, going east of Edom and Moab, and camping on the eastern side of the gorge of the River Arnon. The Arnon is the eastern border of Moab, and since the Israelites didn't cross it, they didn't even set foot in Moab.