(7) Wilt thou go.--So Ahab asks Jehoshaphat in 1Kings 22:4, and he replies as here, "I am as thou art," &c. This indicates that the present section was originally composed by the same hand as 1Kings 20:1-34; 1Kings 22:1-37 (Thenius) Jehoshaphat assented, in spite of the prophetic censures of his alliance with Ahab and Ahaziah (2Chronicles 19:2; 2Chronicles 20:37); perhaps because he was anxious to inflict further punishment on the Moabites for their inroad into Judah (2 Chronicles 20), and to prevent any recurrence of the same (Keil).

Against Moab to battle?--Or, into Moab to the war?

Verse 7. - And he went and sent to Jehoshaphat the King of Judah, saying. Jehoshaphat had originally allied himself with Ahab, and had cemented the alliance by a marriage between his eldest son, Jehoram, and Athaliah, Ahab's daughter (2 Kings 8:18; 2 Chronicles 18:1). He had joined Ahab in his attack on the Syrians at Ramoth-Gilead (1 Kings 22:4-36), and had thereby incurred the rebuke of Jehu the son of Hanani (2 Chronicles 19:2). This, however, had net prevented him from continuing his friendship with the Israelite royal house; he "joined himself with Ahaziah" (2 Chronicles 20:35), Ahab's successor, and though their combined naval expedition met with disaster (1 Kings 22:48), yet he still maintained amicable relations with the Israelite court. Jehoram, therefore, confidently sought his active help when he made up his mind to engage in a war with Moab. 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, and my hones as thy horses. Compare the answer which the same king had made to Ahab, when requested to join him in his attack on the Syrians (1 Kings 22:4). The words were probably a common formula expressive of willingness to enter into the closest possible alliance. Jehoshaphat, it appears from 2 Chronicles 20:1-35, had, a little before this, been himself attacked by the united forces of Moab and Ammon, and brought into a peril from which he was only delivered by miracle. It was, therefore, much to his advantage that Moab should be weakened.

3:6-19 The king of Israel laments their distress, and the danger they were in. He called these kings together, yet he charges it upon Providence. Thus the foolishness of man perverteth his way, and then his heart fretteth against the Lord, Pr 19:3. It was well that Jehoshaphat inquired of the Lord now, but it had been much better if he had done it before he engaged in this war. Good men sometimes neglect their duty, till necessity and affliction drive them to it. Wicked people often fare the better for the friendship and society of the godly. To try their faith and obedience, Elisha bids them make the valley full of pits to receive water. Those who expect God's blessings, must dig pools for the rain to fill, as in the valley of Baca, and thus make even that a well, Ps 84:6. We need not inquire whence the water came. God is not tied to second causes. They that sincerely seek for the dew of God's grace, shall have it, and by it be made more than conquerors.And he went and sent to Jehoshaphat the king of Judah, saying, the king of Moab hath rebelled against me,.... By refusing to pay him tribute:

wilt thou go up with me against Moab to battle? and he said, I will go up; which he agreed to, partly to encourage in the reformation of religion which he had begun, and partly to chastise the Moabites for their invasion of his country, 2 Chronicles 20:1.

I am as thou art, my people as thy people, and my horses as thy horses; the same answer he returned to Ahab; see Gill on 1 Kings 22:4.