2 Kings 9:7
And thou shalt smite the house of Ahab thy master, that I may avenge the blood of my servants the prophets, and the blood of all the servants of the LORD, at the hand of Jezebel. And thou shalt smite the house of Ahab thy master, that I may avenge the blood of my servants the prophets, and the blood of all the servants of the LORD, at the hand of Jezebel.
The charge to strike the house of Ahab was brought to Jehu by Elisha's messenger when Jehu was anointed king of Israel at Ramoth-gilead while in command of the armies. It commissioned him from the Lord to destroy Ahab's house in judgment for the blood of the Lord's servants, including the prophets, shed at Jezebel's hand. That vengeance was to be exacted for Jezebel's killing of the prophets and servants of the Lord. Its commission was carried out against Ahab's surviving family and the leaders of Baal worship, bringing their power in Israel to an end.