all his days: i.e. all the days of Jehoiada. Compare 2 Chronicles 24:14-18. Jehoiada. His uncle. See note on Jehosheba, 2 Kings 11:2.
Related Commentaries of 2 Kings 12:2
2 Kings 12:2
2 And Jehoash did that which was right in the sight of the LORD all his days wherein Jehoiada the priest instructed him.