John Gill Commentary 2 Chronicles 13:4

"And Abijah stood up upon mount Zemaraim, which is in the hill-country of Ephraim, and said, Hear me, O Jeroboam and all Israel:" — 2 Chronicles 13:4 (ASV)

And Abijah stood upon Mount Zemaraim, which is in Mount
Ephraim
Which might have its name from a city of Benjamin of this name, to which it was near, though within the borders of Ephraim, (Joshua 18:22) formerly inhabited by the Zemarites, from whence it might have its name, (Genesis 10:18) here Abijah stood, that he might be the better heard by the armies pitched in the valley; and very probably he desired a parley, and it was granted, otherwise he would not have been safe in the position in which he was;

and said, hear me, thou Jeroboam, and all Israel ;
as many as were now gathered together, and which were a great number.