Apology: My Bible study took a couple of hours, by which time Dottard had posted his answer (which I think is very good). I had prepared my answer in a story-telling format, then hesitated to post it, thinking it would not be sufficiently scholarly for this site. Then I thought, why not share my findings with others? It's a fascinating account with all sorts of lessons to be learned. So, here goes...
Main Characters: Ahab, king of Israel; Jehoshaphat, king of Judah; Micaiah, prophet of the Lord; Zedekiah, a false prophet; Amon, one of Ahab’s high officials; the king of Syria.
Background: 1 Kings chapter 18 informs us that Ahab had gathered 450 prophets of Baal on Mount Carmel to face Elijah, but the 400 prophets of Asherah failed to turn up. Now (in 1 Kings chapter 22) Ahab gathers his 400 prophets before him to ask if he should go into battle against Ramoth-gilead. They reply “Go up, for the Lord will give it into the hand of the king”. Jehoshaphat is unconvinced, perhaps because he knows full well that the king’s prophets are not prophets of the Lord as they claim. He asks if there is not another prophet of the Lord of whom they should inquire. Reluctantly, Ahab summons Micaiah whom he hates because he never prophesies good concerning the king.
Micaiah prophesies against Ahab: After Micaiah sarcastically repeats what the false prophets predicted (victory for Ahab) he then speaks the truth: “I saw all Israel scattered on the mountains, as sheep that have no shepherd. And the Lord said, ‘These have no master; let each return to his home in peace.’” And the king of Israel said to Jehoshaphat, “Did I not tell you that he would not prophesy good concerning me, but evil?” And Micaiah said, “Therefore hear the word of the Lord: I saw the Lord sitting on his throne, and all the host of heaven standing beside him on his right hand and on his left; and the Lord said, ‘Who will entice Ahab, that he may go up and fall at Ramoth-gilead?’ And one said one thing, and another said another. Then a spirit came forward and stood before the Lord, saying, ‘I will entice him.’ And the Lord said to him, ‘By what means?’ And he said, ‘I will go out, and will be a lying spirit in the mouth of all his prophets.’ And he said, ‘You are to entice him, and you shall succeed; go out and do so.’ Now therefore behold, the Lord has put a lying spirit in the mouth of all these your prophets; the Lord has declared disaster for you.” (1 Kings 22:17-23)
The Point: In 1 Kings 22:23-24 Micaiah claims that Zedekiah and his prophets had a lying spirit. Zedekiah responds by declaring that he has been influenced by “the Spirit of the Lord.” Clearly, the Spirit of the Lord could not have been speaking to both Zedekiah and Micaiah. Though God himself does not do evil, sometimes he uses evil agents to accomplish his purposes. If Zedekiah and the false prophets were under the Spirit of the Lord then Ahab had nothing to fear by going into battle. But the lying spirit caused Ahab to doubt the final outcome, hence his disguise. He was trying to work the odds to his advantage, just in case Micaiah was speaking the truth.
Outcome: Ahab is killed in battle, even though he disguised himself while instructing Jehoshaphat to wear his royal robes. The king of Syria had commanded his soldiers to seek out and kill the king of Israel. Initially the captains of the Syrian chariots thought Jehoshaphat was the king of Israel, but his shout (in Judean) was enough to convince them otherwise. It was a random arrow that struck Ahab, inflicting a mortal wound. Ahab died that evening and the events prophesied by Micaiah came to pass, proving that the Spirit of the Lord was upon him.
Conclusion: Ahab deliberately took action to place Jehoshaphat in mortal danger. In battle the king is the number one target of the enemy. By disguising himself, Ahab sought to remain anonymous knowing full well that Jehoshaphat, wearing his royal robes, would become the primary target. How foolish of Ahab to think his disguise would protect him from what the Lord had purposed!
Did Ahab deliberately mislead Jehoshaphat? Ahab’s motives were entirely transparent and selfish, and it is unlikely that Jehoshaphat was misled. Jehoshaphat did not fear for his own life because he he knew that the Spirit of the Lord was upon Micaiah. The outcome of the battle was not in doubt, even though Ahab showed himself to be a doubting, duplicitous coward who was manipulated by the lying spirit.