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
He said, "Come with me, and see my zeal for the Lord." So he had him ride in his chariot.
References for 2 Kings 10:16
When he came to Samaria, he killed all who were left to Ahab in Samaria, until he had wiped them out, according to the word of the Lord that he spoke to Elijah.
Then Jehu assembled all the people and said to them, "Ahab offered Baal small service; but Jehu will offer much more.
Now therefore summon to me all the prophets of Baal, all his worshipers, and all his priests; let none be missing, for I have a great sacrifice to offer to Baal; whoever is missing shall not live." But Jehu was acting with cunning in order to destroy the worshipers of Baal.
Jehu decreed, "Sanctify a solemn assembly for Baal." So they proclaimed it.
Jehu sent word throughout all Israel; all the worshipers of Baal came, so that there was no one left who did not come. They entered the temple of Baal, until the temple of Baal was filled from wall to wall.
He said to the keeper of the wardrobe, "Bring out the vestments for all the worshipers of Baal." So he brought out the vestments for them.
Then Jehu entered the temple of Baal with Jehonadab son of Rechab; he said to the worshipers of Baal, "Search and see that there is no worshiper of the Lord here among you, but only worshipers of Baal."