2 Kings 9:1

We have here the anointing of Jehu to be king, who was, at this time, a commander (probably commander-in-chief) of the forces employed at Ramoth-Gilead, Kg2 9:14. There he was fighting for the king his master, but received orders from a higher king to fight against him. It does not appear that Jehu aimed at the government, or that he ever thought of it, but the commission given him was a perfect surprise to him. Some think that he had been anointed before by Elijah, whom God ordered to do it, but privately, and with an intimation that he must not act till further orders, as Samuel anointed David long before he was to come to the throne: but that it not at all probable, for then we must suppose Elijah had anointed Hazael too. No, when God bade him do these things he bade him anoint Elisha to be prophet in his room, to do them when he was gone, as God should direct him. Here is, I. The commission sent. 1. Elisha did not go himself to anoint Jehu, because he was old and unfit for such a journey and so well known that he could not do it privately, could not go and come without observation; therefore he sends one of the sons of the prophets to do it, Kg2 9:1. They not only reverences him as their father (Kg2 2:15), but observed and obeyed him as their father. This service of anointing Jehu, (1.

— Matthew Henry's Concise Commentary (public domain)