Question: "Why did God use a lying spirit to deceive Ahab?"
Answer: In 1 Kings 22:19-23, there is a troubling passage in which we are told that God used a lying spirit to deceive Ahab. Does God really use evil, lying spirits to do His bidding? Why would God do such a thing? To find the answer to this question, we need to learn a little background about King Ahab, and also understand something about the sovereignty of God.
King Ahab was the son of Omri, and he reigned over Israel in Samaria for 22 years (1 Kings 16:29). Continuing the example of his father, Ahab did evil in the sight of God by worshiping Baal and “did more to provoke the Lord God of Israel than all the kings of Israel that were before him” (1 Kings 16:33). Ahab again and again proved he was bent on evil, evidenced by his continued refusal to listen to the prophet Elijah’s warnings. Ahab accused Elijah of troubling Israel by the drought, but Elijah declared that it was Ahab's own sin that caused the troubles for the nation (1 Kings 18:18). Since Ahab had declared war on God by killing His prophets (v. 13), God then brought the war to Ahab in the form of a contest (1 Kings 18:19-40) between the four hundred and fifty prophets of Baal on one side, and Elijah on the other. When God miraculously verified Elijah’s status as His true prophet, Ahab should have repented, but he remained in his sinful rebellion, fueled by the wicked anger of his wife, Jezebel.
In many subsequent incidents, God again showed His power and mercy to Ahab, but the king refused to submit and obey Him. Finally Jehoshaphat, king of Judah, came to visit him and Ahab persuaded him to join in battle to take Ramoth-Gilead from the Syrians. Wisely, Jehoshaphat insisted that they seek God's will in the matter, so Ahab brought 400 false prophets together, who all assured him that God would give them victory (1 Kings 22:6). Jehoshaphat recognized their falsehood and asked whether a true prophet of God could be summoned. Ahab acknowledged that Micaiah was a true prophet, but he hated him, because “he never prophesies anything good about me, but always bad” (1 Kings 22:8).
Micaiah was brought before the kings and delivered God's final warning to Ahab. He said that if they went to war, they would be defeated and left without a king. Ahab replied, “Didn't I tell you that he never prophesies anything good about me, but only bad?” (1 Kings 22:18). Ahab was again rejecting the clear warning from God, and choosing a path of wicked rebellion. In response to Ahab’s constant choice of sin, God revealed some of the inner workings of the spiritual world.
God had already pronounced a death sentence upon Ahab (1 Kings 20:42, 21:19), but had given him opportunity to repent of his wickedness. With this final rejection of God's counsel, God determined to carry out the death sentence. Since Ahab continued to prefer the lies of his false prophets over the truth given by God's prophets, God chose to use the false prophets to carry out His plan. When God asked for volunteers to “entice Ahab into attacking Ramoth Gilead and going to his death there” (1 Kings 22:20), a spirit (fallen angel/demon) said he would be a lying spirit in the mouth of the prophets. God gave the spirit permission to proceed, and Ahab received the message he desired.
God chose to use a lying spirit because Ahab rejected God's rebukes and warnings all through his life and the cup of God’s wrath was full. Since God is sovereign over all of creation, He is not restricted in what or whom He can use to accomplish His holy purposes. All of creation is under His authority, and He chooses to use people and spirits, both good and evil, to bring His divine plans to pass and bring glory to Himself. “He does as he pleases with the powers of heaven and the peoples of the earth. No one can hold back his hand or say to him: ‘What have you done?’" (Daniel 4:35). In the case of Ahab, God chose to using a lying spirit to accomplish His perfect and righteous plan (Psalm 18:30). The lying spirit will receive its punishment just as Ahab did, and those who repent of their sins will receive forgiveness just like Ahab could have. The real question is, “Will I respond to God's warnings with faith and obedience, or will I reject His counsel and be rejected by Him?”