Numbers 21:13

13 Then they moved out and camped on the far side of the Arnon River, in the wilderness adjacent to the territory of the Amorites. The Arnon is the boundary line between the Moabites and the Amorites.

Numbers 21:13 Meaning and Commentary

Numbers 21:13

From thence they removed, and pitched on the other side of
Arnon
A river on the borders of Moab:

which is in the wilderness that cometh out of the coasts of the
Amorites;
according to Jarchi, they went round the land of Moab, all to the south and east, and came not into the border of Moab, as Jephthah said, ( Judges 11:18 ) but before they came hither they had a station at Almondiblathaim, ( Numbers 33:46 Numbers 33:47 )

for Arnon is the border of Moab, between Moab and the Amorites;
a river which divided these two countries, and bounded them; and Moses is the more particular in this account, to show that the Israelites took nothing from the Moabites, but what the Amorites had taken from them, they being charged not to distress the Moabites and Ammonites, ( Deuteronomy 2:9 Deuteronomy 2:19 ) , see Jephthah's defence, ( Judges 11:15-27 ) .

Numbers 21:13 In-Context

11 Then they went on to Iye-abarim, in the wilderness on the eastern border of Moab.

12 From there they traveled to the valley of Zered Brook and set up camp.

13 Then they moved out and camped on the far side of the Arnon River, in the wilderness adjacent to the territory of the Amorites. The Arnon is the boundary line between the Moabites and the Amorites.

14 For this reason speaks of “the town of Waheb in the area of Suphah, and the ravines of the Arnon River,

15 and the ravines that extend as far as the settlement of Ar on the border of Moab.”