Albert Barnes Commentary 2 Kings 3:7

"And he went and sent to Jehoshaphat the king of Judah, saying, The king of Moab hath rebelled against me: wilt thou go with me against Moab to battle? And he said, I will go up: I am as thou art, my people as thy people, my horses as thy horses." — 2 Kings 3:7 (ASV)

The close alliance between the two kingdoms continued. Jehoram therefore confidently made the same request regarding Moab that his father had made two years before concerning Syria.

Jehoshaphat consented at once, even though his previous compliance had brought him a rebuke from a prophet (2 Chronicles 19:2). Perhaps Jehoram’s removal of Baal worship influenced him (2 Kings 3:2). Jehoshaphat himself had been attacked by the Moabites the previous year, and although the attempt had failed, he would have felt that it might be renewed. It was therefore important to seize the opportunity that now presented itself to weaken his enemy.