What does 2 Kings 10:15 mean?

As Jehu left there, he met Jehonadab son of Rechab, who was coming to meet him. Jehu greeted him and asked, 'Are you with me, as I am with you?' Jehonadab answered, 'I am.' Jehu said, 'If so, give me your hand.' So Jehonadab gave him his hand, and Jehu pulled him up into his chariot. 2 Kings 10:15 - Modern Text Bible

(Jehu seeks support from Jehonadab, a respected religious leader, to legitimize his actions and gain allies.)