1 Kings 19:17 - Joseph Benson’s Commentary on the Old and New Testaments

Him that escapeth the sword of Hazael shall Jehu slay This is not to be understood, as if the sword of Hazael should do execution before the sword of Jehu, and the sword of Jehu before that of Elisha: it only signifies, that God had appointed these three persons to punish the apostate Israelites for their idolatries, and that one or other of them should infallibly execute his judgments upon them: Hazael, however, began to slay them before Jehu was king, 2 Kings 8:28-29; though his cruelty was much increased afterward. Jehu destroyed those, whom Hazael did not, as King Joram himself, and Ahaziah, and all the near relations of Ahab. Elisha is said to slay them, either because he brought down, by his prayers, destruction upon the forty-two children of Beth-el, that idolatrous city, 2 Kings 2:24; or because by God's appointment he inflicted the famine, 2 Kings 8:1; or rather, as the prophets are said to pull down and destroy, what they foretel and declare shall be pulled down, because he threatened and predicted destructive judgments to come upon them. He slew them with the sword that came out of his month, the word of God: like the Branch from the stem of Jesse, he smote them with the rod of his mouth, and with the breath of his lips he slew the wicked, Isaiah 11:4.