Matthew Henry on 2 Kings 12:17–end
When Joash had revolted from God and become both an idolater and a persecutor the hand of the Lord went out against him, and his last state was worse than his first.
I. His wealth and honour became an easy prey to his neighbours. Hazael, when he had chastised Israel (Kg2 10:32), threatened Judah and Jerusalem likewise, took Gath, a strong city (Kg2 12:17), and thence intended to march with his forces against Jerusalem, the royal city, the holy city, but whose defence, on account of its sinfulness, had departed. Joash had neither spirit nor strength to make head against him, but gave him all the hallowed things, and all the gold that was found both in his exchequer and in the treasures of the…
Read the whole note in the consoleJamieson-Fausset-Brown on 2 Kings 12:17
Then Hazael . . . fought against Gath--(See on Ch2 24:23).
Adam Clarke on 2 Kings 12:17
Hazael - fought against Gath, and took it - This city, with its satrapy or lordship, had been taken from the Philistines by David, (see Sa2 8:1, and Ch1 18:1); and it had continued in the possession of the kings of Judah till this time. On what pretense Hazael seized it, we cannot tell; he had the ultima ratio regum, power to do it, and he wanted more territory.
John Gill on 2 Kings 12:17
Then Hazael king of Syria went up and fought against Gath, and took it,.... When Jehoiada was dead, and Jehoash was become an apostate, the Lord suffered the king of Syria to be a scourge to him; who first attacked Gath, and took it, which was formerly one of the principalities of the Philistines, but was subdued by David, and had been in the hands of the Israelites ever since; the king of Syria began with this, as nearest to him, to open the way for what he had further in view:
and Hazael set his face to go up to Jerusalem; he made such preparations, and took such measures, as plainly indicated what his design was.
Keil & Delitzsch