From there they journeyed on and camped on the other side of [the river] Arnon, which is in the wilderness that extends from the boundary of the Amorites; for [the river] Arnon is the boundary of Moab, between Moab and the Amorites.

That is why it is said in the Book of the Wars of the Lord:

“Waheb in Suphah,
And the wadis of the Arnon [River],

Then Israel struck the king of the Amorites with the edge of the sword and took possession of his land from the Arnon to the Jabbok, as far as the Ammonites, for the boundary of the Ammonites was strong.

For Heshbon was the city of Sihon, king of the Amorites, who had fought against the former king of Moab and had taken all his land out of his hand, as far as the Arnon.

“For fire has gone out of Heshbon,
A flame from the city of Sihon;
It devoured Ar of Moab
And the lords of the heights of the Arnon.

When Balak heard that Balaam was coming, he went out to meet him at the city of Moab, which is on the border at the Arnon [River], at the farthest end of the border.