If we sow obedience, in time we reap understanding. But if we sow disobedience, we reap madness, blindness, and confusion of heart (see Deuteronomy 28:28-29). Psalm 19:8 shows this same relationship: “. . . the commandment of the LORD is pure, enlightening the eyes.” When we uphold the commandments, our understanding becomes more precise. But the inverse is also true: When we break the commandments, our eyes become darkened, yet like the Pharisees, we may still proclaim, “We see” (John 9:41).

This cause-and-effect relationship underscores the seriousness of sin. We know that the wages of sin is death (Romans 6:23), but the above verses teach that sin also degrades a sinner's understanding. This principle illustrates the foolishness of thinking one can sin now and repent later, banking on God's forgiveness. Yes, God forgives sins that are not willful (see Hebrews 10:26-27), removing the death penalty, but He may not remove other effects of sin right away, if at all. Among these effects is sin's influence on the mind. Repentance does not restore everything to where it was before the sin.

The natural law in these verses also illuminates why the Bible refers to sin as a snare: It is far easier to get into a snare than out. When we sin, we lose some measure of understanding, at least for a time. This blurred state of mind makes it easier to make another wrong decision. That next sin then further blinds or clouds our judgment, making it easier to stumble yet again—and on it goes because sin has a terrible power to draw one in deeper. Because of our relationship with God, we have tremendous help in overcoming, but sin still entangles and blinds even the converted because that is sin's nature. Sin causes blindness, and blindness causes sin.