Keeping a Pure Mind


(from MacArthur’s The Vanishing Conscience)

The Bible clearly teaches that sin goes beyond behavior. Sinful behavior always starts with sinful thinking in the mind. Someone may think that as long as his thoughts are not acted out he has not sinned, or that sins of the mind are not as bad as sins acted out. This is not true. Lust itself is sinful, as is greed, covetousness (note Commandment #10), pride and hatred. In fact, thoughts and fantasies can be just as sinful as sinful deeds.

Texts: Matt 5:21-22, 27-28; 15:18-19; 23:25-28

If you want to progress in sanctification, start by controlling your thought-life. Controlling your thoughts is extremely important; your thoughts are the frontlines of the battle for holiness. Remember that evil deeds are the offspring of evil thoughts.

How does one sin with his mind?

  1. Sins of remembering: remembering, cherishing, or mentally reliving past sins. Sin has a way of impressing itself on your memory. When you bring back and think about past sin, you repeat the sin. [This is one reason porn is so destructive: once you implant an image in you brain, it’s easy to bring it back up and difficult to forget it. It’s not just images, either. Sinful/explicit dialogue and stories are the same. Often our imaginations fill in more explicitly than a pix would. This is one reason we need to stay away from such material. If it never gets into your brain, you’ll never remember it.]
  2. Sins of scheming or plotting: planning sinful actions is sin. Ps 36:1-4; Prov 15:26, 24:8-9 Those who plot evil actions reveal the wickedness filling their hearts. Even if the plans never are acted out, God condemns the sinful thoughts.
  3. Sins of imagining: fantasizing about sinful activity. This is what Jesus referred to in Mt 5:28. Even if you don’t plan on acting out the thoughts, if you imagine it, you’ve sinned and you’re guilty. [Imagination is usually far worse than that which we’d actually do. Eg., comments of guys at Patio when a good-looking woman comes in. ]

How to Deal with Evil Thoughts

  1. Confess and forsake known sin (Isa 55:7). If you are guilty of mental sins, repent of it and ask forgiveness. Don’t downplay the sinfulness of evil thoughts. Remember that God knows your thoughts (Ps 139:2-4). God hates this sin as much as any other.

  2. Refuse to entertain sinful thoughts. Who controls what you think about? You do. Don’t let yourself dwell on sinful images or ideas. Don’t read books, look at images, or listen to music that generate sinful thoughts or tempt you to indulge in them (Job 31:1). Stay away from things that tempt you in this way. Guard your thoughts. This requires discernment: the ability to evaluate something before giving or withholding approval. E.g., lots of bad stuff on the internet, most easily accessible. If you can’t handle the temptation, stay away from it.]

  3. Focus on the right kind of thoughts (Phil 4:8). Soak your mind with true, valuable, honorable, and pure information. Replace the bad with the good. [Many sources: Bible, classic novels, good magazines, some TV shows, etc. Unfortunately, replacement doesn’t get rid of the bad stuff.]

  4. Feed on the Word (Ps 119:11). The Word strengthens and insulates your mind. It also reveals your sin and shows you the right way to go.

  5. Get accountable. If you find you have difficulty with this on your own, find someone you can check in with occasionally who will help you keep you mind on the right track.

Conclusion: Sin always starts in the mind. You are in control of what you think about. Determine to think about the right things. Don’t fill your mind with trash. When you do commit mental sins, repent of it and determine not to let it happen again.


  1. Thank you for haring this information with me! I haven't gone to Sunday School in quite a while. I wish I had payed attention though, but now, I'm going to try my best to become a better person.
    I keep sinning in my mind, and I thought it didn't matter. But this changes everything. Thank you!

  2. thank you. How do you not think about someone you deeply care about….possibly even love. I think of everything including what it would be like to marry this person. I need help!

  3. Hi Melissa, excellent question. First, deep caring/love and the feelings that surround them are appropriate and God-given. They should be viewed positively as His gifts. Not knowing the specificity of your thoughts (which we do not want you to share), I can only comment generically…

    Here are a few things I would think about to sort through good and evil thoughts:
    — thank God for giving you this awesome emotion. God loves and He was willing to create you with the capacity to love as well.
    —if your feelings are not reciprocated, are you prepared to deal with anger and disappointment?
    —is this person someone you should biblically love?
    —are you obsessed with these thoughts that you have become unproductive?

    This following practice has helped me and others. Take a 3×5 card and divide both front and back into four areas (total of 8). At the top of each area, put one trait from Philippians 4:8. Then under each trait write a couple of ideas to reflect on throughout the day…For example:

    Think on things that are "true."
    –I am not married to this person, so I have to keep my feelings and emotions "in check."
    –Love is God-given so I am to thank God for this wonderful emotion

    …so on and so forth…

  4. After going over this lesson I knew this was something I had to teach at church to put Youth Sunday school class!!! And not just for them. But I learned o much more.

  5. This is a great lesson! I can't wait to share it with my sunday school class! Thanks! =)

  6. This is just what I've been looking for! I am going to share this lesson with my teenagers in our next Sunday School Class.

  7. Courtney K. says:

    great message! excited to use it tomorrow! great reminder.

  8. thank you and may God almighty bless you…. my mind has been my battlefield and the more i fight the more i saw it but i just wrote down on my palm “You are in control of what you think”

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