Jamieson, Fausset and Brown on 2 Chronicles 24:15-16

15-16. Jehoiada waxed old ... and died--His life, protracted to unusual longevity and spent in the service of his country, deserved some tribute of public gratitude, and this was rendered in the posthumous honors that were bestowed on him. Among the Hebrews, intramural interment was prohibited in every city but Jerusalem, and there the exception was made only to the royal family and persons of eminent merit, on whom the distinction was conferred of being buried in the city of David, among the kings, as in the case of Jehoiada.

2Ch 24:17-22. Joash Falls into Idolatry.