C. F. Keil and Franz Delitzsch on 2 Kings 13:19

2Ki 13:19

Elisha was angry at this, and said: “Thou shouldst shoot five or six times, thou wouldst then have smitten the Syrians to destruction; but now thou wilt smite them three times.” להכּות: it was to shoot, i.e., thou shouldst shoot; compare Ewald, §237, c.; and for הכּית אז, then hadst thou smitten, vid., Ewald, §358, a. As the king was told that the arrow shot off signified a victory over the Syrians, he ought to have shot off all the arrows, to secure a complete victory over them. When, therefore, he left off after shooting only three times, this was a sign that he was wanting in the proper zeal for obtaining the divine promise, i.e., in true faith in the omnipotence of God to fulfil His promise.“When the king reflected upon the power of the kings of Syria, since he had not implicit faith in Elisha, he thought that it was enough if he struck the earth three times, fearing that the prophecy might not be fulfilled if he should strike more blows upon the ground.” - Clericus.

Elisha was angry at this weakness of the king’s faith, and told him that by leaving off so soon he had deprived himself of a perfect victory over the Syrians.