But Amaziah would not hear. Therefore Jehoash king of Israel went up; and he and Amaziah king of Judah looked one another in the face at Bethshemesh, which belongeth to Judah.

Jamieson-Fausset-Brown Bible Commentary

11-14. But Amaziah would not hear-The sarcastic tenor of this reply incited the king of Judah the more; for, being in a state of judicial blindness and infatuation (2Ch 25:20), he was immovably determined on war. But the superior energy of Joash surprised him ere he had completed his military preparations. Pouring a large army into the territory of Judah, he encountered Amaziah in a pitched battle, routed his army, and took him prisoner. Then having marched to Jerusalem [2Ki 14:13], he not only demolished part of the city walls, but plundered the treasures of the palace and temple. Taking hostages to prevent any further molestation from Judah, he terminated the war. Without leaving a garrison in Jerusalem, he returned to his capital with all convenient speed, his presence and all his forces being required to repel the troublesome incursions of the Syrians.

Matthew Henry's Concise Commentary

14:8-14 For some time after the division of the kingdoms, Judah suffered much from the enmity of Israel. After Asa's time, it suffered more by the friendship of Israel, and by the alliance made with them. Now we meet with hostility between them again. How may a humble man smile to hear two proud and scornful men set their wits on work, to vilify and undervalue one another! Unholy success excites pride; pride excites contentions. The effects of pride in others, are insufferable to those who are proud themselves. These are the sources of trouble and sin in private life; but when they arise between princes, they become the misery of their whole kingdoms. Jehoash shows Amaziah the folly of his challenge; Thine heart has lifted thee up. The root of all sin is in the heart, thence it flows. It is not Providence, the event, the occasion, whatever it is, that makes men proud, secure, discontented, or the like, but their own hearts do it.