Matthew 18:9 says if your eye causes you to sin then its better to get to heaven with one eye than to go to hell with both eyes. Our eyes can cause us to sin by looking at the things we cannot have. We look and linger, it causes sin, whether that it's that we want what doesn't belong to us or we get angry over what we see. To keep looking makes us roll over in our heads how we can get that thing. Our eyes are the window to our soul, and if our eye is dark, how dark our whole soul must be. We must be careful with our eyes.