Matthew Poole and continuators on 2 Samuel 24:5

5 ¶ And they passed over Jordan , and pitched in Aroer, on the right side of the city that lieth in the midst of the river of Gad , and toward Jazer .

They began their Computation in the Eastern part of David's Dominions, which were beyond Iordan.

Or, encamped. For Ioab carried with them divers of his Commanders, and others; partly, for his Honour, and the credit of the Work: partly, to assist him in that troublesom Work: and partly, to overcome the People, in case they should Oppose it as sinful or burdensome, or favouring of some Evil Design which David might have upon them.

i. e. Of the River which lay in the Tribe of Gad, or upon the borders of Gad and Reuben, which was called Arnon, Deut. 2. 36.

Or, near Iazer, which also was upon the River Arnon.

Marginal references: Or, Valley.