Of which see on 1 Kings 22:4. He joins with him in this war, partly because the war was very just in itself, and convenient for Jehoshaphat, both in the general, that rebels and revolters should be chastised and suppressed, lest the example should pass into his dominions, and the Edomites should be hereby encouraged to revolt from him, as they did from his son; and in particular, that the Moabites should be humbled, who had with others invaded his land before this time, 2 Chronicles 20:1, and might do so again if they were not brought low, for which a fair opportunity was now offered to him; and partly because Jehoram had reformed some things, and Jehoshaphat hoped by this means to engage him to proceed further in that work.
Related Commentaries of 2 Kings 3:7
2 Kings 3:7
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, and my horses as thy horses.