2 Kings 11:21 Joash was seven years old when he began to reign.

2 Kings 12:1-2 In the seventh year of Jehu, Joash became king and he reigned in Jerusalem forty years. His mother's name was Zibiah; she was from Beersheba. Joash did what was right in the eyes of the Lord all the years Jehoiada the priest instructed him.