An intrusive thought is an involuntary, unwanted image, phrase, or impulse. They are very common; nearly everyone has them from time to time. Sometimes they are of a violent nature, other times they are sexual. Often they are blasphemous or induce great fear of having done a ritual incorrectly. They can be quite disconcerting, especially when they are completely contrary to what a person actually believes.
Is it a sin to have intrusive thoughts?
Psalm 139:2 says, "You know when I sit down and when I rise up; you discern my thoughts from afar." God knows our thoughts, and He knows how insubstantial they can be (Psalm 94:11). But we tend to forget that He also knows the intent behind our thoughts. He knows the wicked will blaspheme His name—"In the pride of his face the wicked does not seek him; all his thoughts are, 'There is no God'" (Psalm 10:4), but He is always prepared to forgive (Isaiah 55:7). God knows that Christians can have intrusive thoughts as well. He looks deeper than the fleeting image, "…for the LORD searches all hearts and understands every plan and thought," (1 Chronicles 28:9). He is easily able to judge between a thought, a belief, and an intent (Hebrews 4:12).
God also has a plan to prevent intrusive thoughts. Intrusive thoughts are not necessarily sin, but the actions we take leading up to the thought may be. If we fill our minds with ungodly things, blasphemous and harmful thoughts will be more likely to come up. Philippians 4:8 tells us, "Finally, brothers, whatever is true, whatever is honorable, whatever is just, whatever is pure, whatever is lovely, whatever is commendable, if there is any excellence, if there is anything worthy of praise, think about these things." And even if our actions led to the thought, God will be our consolation (Psalm 94:19).
Second Corinthians 10:3-5 details how to take control of intrusive thoughts. First, relax and realize that intrusive thoughts cannot be completely conquered by earthly methods. Spontaneous blasphemy and harmful inclinations are aspects of spiritual warfare. Next, take the thought captive—capture it, break it down, determine if there is any truth in it, and vanquish the lies. Study and memorize Scripture so that you can be ready with the truth the next time the thought pops up. Analyze your own heart, and submit any part of you that believes the lie. Pray David's prayer from Psalm 139:23-24: "Search me, O God, and know my heart! Try me and know my thoughts! And see if there be any grievous way in me, and lead me in the way everlasting!" You may have to do this many, many times, but, eventually, the lie should fade as you concentrate on God's truth (Psalm 1:1-3).
Sometimes repeatedly capturing the thought and refuting it with God's Word doesn't work. Sometimes, intrusive thoughts can be overwhelming and impossible to control. This is one of the primary symptoms of obsessive compulsive disorder and a lesser symptom of many other disorders. If the intrusive thoughts are particularly debilitating, the person should see a medical doctor or a qualified counselor. God has provided us with physicians who can care for the body as well as the soul, and we should take advantage of their expertise.
Is there an unpardonable sin? What is it?
How do I control my thoughts?
How do I get control of sinful impulses?
How can I know what is a sin and what isn't?
What does the Bible say about edification? Why is it so important for Christians?
Truth about Sin