The "valley of Zephathah" - not elsewhere mentioned - is probably the broad Wady which opens out from Mareshah (marginal reference) in a northwesterly direction, leading into the great Philistine plain. Zerah, on the advance of Asa, drew off into the wider space of the Wady, where he could use his horsemen and chariots.

Then Asa went out against him,.... Notwithstanding he brought so great an army with him:

and they set the battle in array in the valley of Zephathah at Mareshah; where the Ethiopians were; he did not stay till they got further into his country, but marched against them when on the frontiers of it, and chose the valley to pitch in, as being more to the advantage of his smaller army; see Judges 1:17.

Then he called upon the Lord his God for help. וגו עמּך אין we translate, with Berth., "None is with Thee (on עמּך, cf. 2 Chronicles 20:6; Psalm 73:25) to help between a mighty one and a weak," i.e., no other than Thou can help in an unequal battle, i.e., help the weaker side; while the Vulg., on the contrary, after the analogy of 1 Samuel 14:6, translates, "non est apud te ulla distantia, utrum in paucis auxilieris an in pluribus;" and the older commentators (Schmidt, Ramb.) give the meaning thus: "perinde est tibi potentiori vel imbecilliori opem ferre." But in 1 Samuel 14:16 the wording is different, so that that passage cannot be a standard for us here. "In Thy name (i.e., trusting in Thy help) are we come against this multitude" (not "have we fallen upon this multitude"). וגו יעצר אל, "Let not a mortal retain strength with Thee" (עצר equals כּח עצר, 2 Chronicles 13:20; 1 Chronicles 29:14), i.e., let not weak men accomplish anything with Thee, show Thy power or omnipotence over weak men.

Then Asa went out against him, and they set the battle in array in the valley of Zephathah at Mareshah.

10. Then Asa went out against him, and they set the battle in array . at Mareshah-one of the towns which Rehoboam fortified (2Ch 11:8), near a great southern pass in the low country of Judah (Jos 15:44). The engagement between the armies took place in a plain near the town, called "the valley of Zephathah," supposed to be the broad way coming down Beit Jibrin towards Tell Es-Safren [Robinson].

14:1-15 Asa's piety, He strengthens his kingdom. - Asa aimed at pleasing God, and studied to approve himself to him. Happy those that walk by this rule, not to do that which is right in their own eyes, or in the eye of the world, but which is so in God's sight. We find by experience that it is good to seek the Lord; it gives us rest; while we pursue the world, we meet with nothing but vexation. Asa consulted with his people how to make a good use of the peace they enjoyed; and concluded with them that they must not be idle, nor secure. A formidable army of Ethiopians invaded Asa's kingdom. This evil came upon them, that their faith in God might be tried. Asa's prayer is short, but it is the real language of faith and expectation from God. When we go forth in God's name, we cannot but prosper, and all things work together for the good of those whom he favours.