Albert Barnes Commentary 2 Kings 13:19

"And the man of God was wroth with him, and said, Thou shouldest have smitten five or six times: then hadst thou smitten Syria till thou hadst consumed it, whereas now thou shalt smite Syria but thrice." — 2 Kings 13:19 (ASV)

Human unfaithfulness limits the goodness of God. Although Joash obeyed the prophet’s command, he did so without zeal or fervor, and likely without any sincere belief in the effectiveness of his actions .

God had been willing to give Israel a complete victory over Syria (2 Kings 13:17). However, by failing to embrace the divine promise in its fullness, Joash restricted the outflow of mercy. As a result, the original promise could not be fulfilled.