Assyrian history records another war involving Ahab, which appears to have taken place during the three-year truce with Syria (1 Kings 22:1 1 Kings 22:1And they continued three years without war between Syria and Israel.
American King James Version×). The Assyrians began to rise in power, and made an advance toward the coastal area far north of Israel. Apparently Ahab joined an alliance of nations in repelling their advance, and, according to the inscriptions of Shalmaneser III, he supplied about one half (2,000) of the chariots and perhaps a sixth (10,000) of the infantry.
Jehoshaphat also forms an alliance with Ahab. As part of the alliance, their children, Jehoram and Athaliah, are married (2 Chronicles 18:1 2 Chronicles 18:1Now Jehoshaphat had riches and honor in abundance, and joined affinity with Ahab.
American King James Version×; 2 Chronicles 21:6 2 Chronicles 21:6And he walked in the way of the kings of Israel, like as did the house of Ahab: for he had the daughter of Ahab to wife: and he worked that which was evil in the eyes of the LORD.
American King James Version×). Jehoshaphat pays a visit to his ally, and Ahab proposes that Jehoshaphat join him in an attempt to recover Ramoth-Gilead from the Syrians in yet a third war with them. This was a town on the east side of the Jordan that belonged to Gad and had originally been designated as a city of refuge (Deuteronomy 4:41-43 Deuteronomy 4:41-43  Then Moses severed three cities on this side Jordan toward the sun rise;  That the slayer might flee thither, which should kill his neighbor unawares, and hated him not in times past; and that fleeing to one of these cities he might live:  Namely, Bezer in the wilderness, in the plain country, of the Reubenites; and Ramoth in Gilead, of the Gadites; and Golan in Bashan, of the Manassites.
American King James Version×).
Jehoshaphat agrees but insists on finding out God's will in the matter first. For some reason, when asked about a prophet of God, Ahab does not mention Elijah or his assistant Elisha. Perhaps they were known to be away and not available. In any case, though many true prophets had been killed earlier in Ahab's reign, there were still a few around. Here we are introduced to the prophet Micaiah, who is mentioned nowhere else in Scripture unless, as some have speculated, he is the same Micaiah sent out by Jehoshaphat to teach in Judah (2 Chronicles 17:7 2 Chronicles 17:7Also in the third year of his reign he sent to his princes, even to Benhail, and to Obadiah, and to Zechariah, and to Nethaneel, and to Michaiah, to teach in the cities of Judah.
American King James Version×). One of the saddest aspects of this encounter is that Jehoshaphat, too, is persuaded to ignore the message from the prophet of God whom he had specifically asked to hear from.
Remarkably, we get a glimpse in our current reading of how God actually sometimes uses even demons to fulfill His purposes. Notice that God did not command any spirit here to lie. He simply asked who would do it and told the volunteer to go do what he was inclined to do anyway. The fact that Micaiah's true prophecies were always at odds with those of Ahab's prophets (compare 1 Kings 22:8 1 Kings 22:8And the king of Israel said to Jehoshaphat, There is yet one man, Micaiah the son of Imlah, by whom we may inquire of the LORD: but I hate him; for he does not prophesy good concerning me, but evil. And Jehoshaphat said, Let not the king say so.
American King James Version×) would seem to imply that a "lying spirit" was commonly behind the words of Ahab's prophets.
Notice this from The Bible Reader's Companion: "Did God Himself lie to Ahab? Not at all. He did permit Ahab's prophets to lie…. [But] God in fact clearly revealed to Ahab the source of his prophets' predictions, and the truth about what would happen to him in the coming battle. Ahab's death resulted from refusing to believe the truth, not from a failure to know it. Let's be careful not to blame God for the consequences of our own fully conscious choices" (note on 1 Kings 22).