The rest of the acts of Abijah, his ways and his sayings, are written in the story of the prophet Iddo.
We do not find that Jeroboam offered to make any answer at all to Abijah's speech. Though it was much to the purpose, he resolved not to heed it, and therefore he heard it as though he heard it not. He came to fight, not to dispute. The longest sword, he thought, would determine the matter, not the better cause.
Commenting on 2 Chronicles 13:13-22
Written in the story - במדרש bemidrash, "in the commentary;" this, as far as I recollect, is the first place where a midrash or commentary is mentioned. The margin is right. His ways, and his sayings - The commentary of the prophet Iddo is lost.
2Ch 13:22 As to the מדרשׁ of the prophet Iddo, see the Introduction. 13:23 (2Ch 14:1). This is remarked here, because this rest was also a result of Abijah’s great victory over Jeroboam.