2 Chronicles 25:5
Moreover Amaziah gathered Judah together, and made them captains over thousands, and captains over hundreds, according to the houses of their fathers, throughout all Judah and Benjamin: and he numbered them from twenty years old and above, and found them three hundred thousand choice men, able to go forth to war, that could handle spear and shield.
The history from 2 Chronicles 25 onward covers the same ground as Kings and gives fuller detail on the kings of Judah. It belongs to the reign of Amaziah of Judah, the disloyal king who followed Joash and was followed by Azariah, or Uzziah. The verse records Amaziah gathering Judah together for war against Edom, organizing the men of Judah and Benjamin by their ancestral families under captains over thousands and captains over hundreds, and numbering 300,000 choice men from twenty years old and above who were fit to go forth to war and skilled in handling spear and shield. He numbered this own army without first consulting God.
To that force he added 100,000 hired mighty men of valor from alienated Israel for 100 talents of silver. God sent a man of God with instruction forbidding the use of Israel, because the Lord was not with Ephraim or Israel. In this account Israel stands for all aliens in all time who are excluded from doing God's chosen work with His chosen ones. Amaziah obeyed by dismissing the hired Ephraimites at the loss of the 100 talents, accepted the loss of the payment, and prevailed over Edom without Israel, showing he could go to battle without that hired force and that the Lord is able to give much more than money lost in obedience.
Human numbers, discipline, efficiency, wealth, and allied forces do not decide material contests, for God has power to help and to cast down and the battle is His; leaning on arms of flesh and self-reliance brings a fall, while obeying God and sending home forbidden helpers brings success. After prevailing over Edom, though unstable, Amaziah fell into idolatry by adopting the defeated people's gods, which could not save them, and brought God's anger upon himself. His course contrasts with Jehoshaphat's in response to prophetic counsel: he accepted the prophet's testimony when it pleased him but rejected it when the prophet reproved his actions, and his refusal to heed counsel led to the declaration that God had determined to destroy him because he had acted as he did. The account warns that victory and national strength do not justify turning from God. The verse is a warning against joining with unfaithful allies to advance a cause called Christian and against relying on an army with which God is not present.