Abijah went into battle with an army of 400,000 chosen men, while Jeroboam drew up in formation against him with 800,000 chosen and mighty men of valor.
Abijah's mother was called Maachah, the daughter of Absalom, Ch2 11:20; here she is called Michaiah, the daughter of Uriel. It is most probable that she was a grand-daughter of Absalom, by his daughter Tamar (Sa2 14:27), and that her immediate father was this Uriel. But we are here to attend Abijah into the field of battle with Jeroboam king of Israel. I.
Commenting on 2 Chronicles 13:1-12
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, Jos 18:22 formerly inhabited by the Zemarites, from whence it might have its name, Gen 10:18 here Abijah stood, that he might be the better heard by the armies pitched...
Abijah set the battle in array--that is, took the field and opened the campaign. with . . . four hundred thousand chosen men . . . Jeroboam with eight hundred thousand--These are, doubtless, large numbers, considering the smallness of the two kingdoms.