“You have heard that it was said to those of old, ‘You shall not commit adultery.’  But I say to you that whoever looks at a woman to lust for her has already committed adultery with her in his heart.”
Matthew 5:27-29 NKJV
The Old Testament teaches us about sin, but here Jesus takes it up a notch. We know from the Old Testament that murder is a sin, but Jesus tells us that just thinking about committing murder is sin. And this goes for all the other sins as well. It is a sin to think about cheating on a test. It is a sin to think hateful things about your brothers and sisters, even if you don’t say them out loud. Mental sin is sin.
Jesus says to throw away our eye if it’s causing us to sin. He does not want us to actually go gouge out our own eye, but He uses this language to convey the seriousness of mental sins. It would be better to lose an eye than to go to hell because our mental sins kept us away from God.
Folks, we can control our thoughts. God gives us the strength to do this. It is not easy, and it takes time and effort to learn to control our minds. But with God’s help, we can keep our minds pure.