Matthew Poole and continuators on 2 Chronicles 13:4

4 And Abijah stood up upon mount Zemaraim , which is in mount Ephraim, and said, Hear me, thou Jeroboam, and all Israel.

Some commodious Place whence his Voice might be heard by Jeroboam and some of his Host, who possibly were pitched in the Valley. Or, the two Armies being pitched near to one another, Abijah might desire a Parly before they fought; whereupon Jeroboam and some of his Commanders and Souldiers might draw near to him and stand below him at the bottom of the Hill where they might hear his Speech: which Jeroboam was the more willing to do, that in the mean time he might cause an Ambushment to come behind Abijah and his Army, as he did, v. 13. whilest he was quietly standing before them and seemed to hearken to any Terms of Accommodation which might be offered.