So the steward of the palace, and the governor of the city, along with the elders and the guardians, sent word to Jehu: "We are your servants; we will do anything you say. We will not make anyone king; do whatever you think right."
Then he wrote them a second letter, saying, "If you are on my side, and if you are ready to obey me, take the heads of your master's sons and come to me at Jezreel tomorrow at this time." Now the king's sons, seventy persons, were with the leaders of the city, who were charged with their upbringing.
When the letter reached them, they took the king's sons and killed them, seventy persons; they put their heads in baskets and sent them to him at Jezreel.
When the messenger came and told him, "They have brought the heads of the king's sons," he said, "Lay them in two heaps at the entrance of the gate until the morning."
Then in the morning when he went out, he stood and said to all the people, "You are innocent. It was I who conspired against my master and killed him; but who struck down all these?
Know then that there shall fall to the earth nothing of the word of the Lord, which the Lord spoke concerning the house of Ahab; for the Lord has done what he said through his servant Elijah."
So Jehu killed all who were left of the house of Ahab in Jezreel, all his leaders, close friends, and priests, until he left him no survivor.
Then he set out and went to Samaria. On the way, when he was at Beth-eked of the Shepherds,
Jehu met relatives of King Ahaziah of Judah and said, "Who are you?" They answered, "We are kin of Ahaziah; we have come down to visit the royal princes and the sons of the queen mother."
He said, "Take them alive." They took them alive, and slaughtered them at the pit of Beth-eked, forty-two in all; he spared none of them.
When he left there, he met Jehonadab son of Rechab coming to meet him; he greeted him, and said to him, "Is your heart as true to mine as mine is to yours?" Jehonadab answered, "It is." Jehu said, "If it is, give me your hand." So he gave him his hand. Jehu took him up with him into the chariot.
References for 2 Kings 10:15