Joash starts reigning seven years into Jehu's reign and continues for forty years. He ends up being one of the somewhat rare good kings, since Jehoiada guides him.
However, he still doesn't end worship at the high places—which the narrator thinks needs to go.
Joash orders the priests to use the donations they collect at the Temple to make repairs on it.
By the twenty-third year of Joash's reign, they still haven't made repairs. So Joash tells them not to collect any more donations until they've made the repairs.
But the priests agree not to take donations or make the repairs.
Yet, Jehoiada takes a chest and puts a hole in it and sets it by the altar as a collection box.
When it fills up with money, the priests use it to finally repair the temple. They give it to carpenters, masons, stonecutters, and also use it to by wood and stone.
But they don't make any vessels of gold or anything like that for the Temple. The money that would've been used for that is used to help pay the workers.
The whole process goes smoothly and honestly. The priests are able to keep the money from "sin and guilt offerings" at the Temple for themselves.
A Momentarily Successful Bribe
Meanwhile, the wicked King Hazael of Aram threatens to destroy Jerusalem. But Joash gives him all the gold from the treasuries of the temple, along with the votive gifts of his ancestors (the kings of Judah) and his own votive gifts.
Unfortunately, after forty years of rule, Joash's servants—Jozacar and Jehozabad— conspire and assassinate him.
Joash is buried with David and his other ancestors and is succeeded by his son, Amaziah.