Albert Barnes Commentary Numbers 22:1

"And the children of Israel journeyed, and encamped in the plains of Moab beyond the Jordan at Jericho." — Numbers 22:1 (ASV)

The plains - Hebrew ערבה ‛ ărābâh; the word is the plural of the term used to denote the entire depressed tract along the Jordan and the Dead Sea, and onward, where it is still called the Arabah (Compare to Numbers 21:4 note), to the Elanitic gulf.

On this side Jordan by Jericho - Rather, across the Jordan of Jericho, that is, that part of the Jordan which skirted the territory of Jericho. This form of expression indicates the site of the camp in its relation to the well-known city of Jericho. See Deuteronomy 1:1.