Commentary on the Bible, by Adam Clarke, [1831], at sacred-texts.com
Asa succeeds his father Abijah, reigns piously, and has peace for ten years, Ch2 14:1. He makes a great reformation in Judah, and builds cities of defense, Ch2 14:2-7. His military strength, Ch2 14:8. He is attacked by Zerah the Ethiopian, with an immense army; Asa cries to the Lord, attacks the Ethiopians, and gives them a total overthrow, Ch2 14:9-12. He takes several of their cities, their cattle, etc., and returns to Jerusalem, laden with spoils, Ch2 14:13-15.
The land was quiet ten years - Calmet thinks these years should be counted from the fifth to the fifteenth of Asa's reign.
Did that which was good - He attended to what the law required relative to the worship of God. He was no idolater, though, morally speaking, he was not exempt from faults, Kg1 15:14. He suppressed idolatry universally, and encouraged the people to worship the true God: see Ch2 14:3-5.
Fenced cities - To preserve his territories from invasion, and strengthen the frontiers of his kingdom, see Ch2 14:7.
Targets and spears - Probably targets with the dagger in the center, and javelins for distant fight.
Bare shields and drew bows - They were not only archers, but had shield and sword for close fight.
Zerah the Ethiopian - Probably of that Ethiopia which lay on the south of Egypt, near to Libya, and therefore the Libyans are joined with them, Ch2 16:8.
A thousand thousand - If this people had come from any great distance, they could not have had forage for such an immense army.
Whether with many - The same sentiment as that uttered by Jonathan, Sa1 14:6, when he attacked the garrison of the Philistines.
O Lord our God - we rest on thee - "Help us, O Lord our God; because we depend on thy Word, and in the name of thy Word we come against this great host." - Targum.
There was - much spoil in them - These cities being on the rear of this vast army, they had laid up much forage in them; and to get this the Jews overthrew the whole.
Tents of cattle - Those which had carried the baggage of the great army, and which they had left in such places as abounded with pasture. Perhaps sheepfolds, enclosures for camels, mules, etc., may also be intended. The discomfiture was great, because God fought for the people; and the spoil was immense, because the multitude was prodigious, indeed almost incredible, a million of men in one place is almost too much for the mind to conceive, but there may be some mistake in the numerals: it is evident from the whole account that the number was vast and the spoil great.