Charles Ellicott Commentary 2 Chronicles 13:3

"And Abijah joined battle with an army of valiant men of war, even four hundred thousand chosen men: and Jeroboam set the battle in array against him with eight hundred thousand chosen men, who were mighty men of valor." — 2 Chronicles 13:3 (ASV)

Set the battle in array. — Began the battle. Vulgate, “cumque iniisset Abia certanien” (1 Kings 20:14).

Four hundred thousand chosen men. —In David’s census, Judah mustered 470,000 fighting men, and Israel 1,100,000, without reckoning Levi and Benjamin (1 Chronicles 21:5). The numbers of the verse present a yet closer agreement with the results of that census as reported in 2 Samuel 24:9; where, as here, the total strength of the Israelite warriors is given as 800,000, and that of Judah as 500,000. This correspondence makes it improbable that the figures have been falsified in transmission. (See Note on 2 Chronicles 13:17.)

Jeroboam also set the battle in array. — While Jeroboam had drawn up against him. Vulgate, instruxite contra aciem.