As soon as the kingdom was confirmed in his hand - No doubt those wicked men, Jozachar and Jehozabad, who murdered his father, had considerable power and influence; and therefore he found it dangerous to bring them to justice, till he was assured of the loyalty of his other officers: when this was clear, he called them to account, and put them to death.
The phrase, “confirmed in his hand” 2 Kings 15:19, usually expresses the authorisation of a new reign by an imperial superior (see 2 Kings 15:19 note); but here it describes the result when the troubles consequent upon the murder of Joash had passed away. The new king‘s authority was generally recognized by his subjects.