In the original Karate Kid movie, the main character entered his penultimate match with an injured knee. The antagonist’s coach advised his fighter, “Sweep the knee. No mercy.” A boxer who sees a gash over his opponent’s eye makes the effort to exploit it to his advantage.
In the fight for our souls, the devil will not stop to exploit every advantage he sees. Should we be surprised that he fights dirty? He shows no mercy; he hits us where we already hurt.
Such is the nature of our enemy. And, that’s the essence of sin and the guilt of sin. Guilt is an injury to our soul that exposes us to further pain. Isaiah felt the pain of his sin most acutely in his mouth. So intense was his guilt that he called woe and ruin on himself. How could a man like Isaiah speak of the purity of the Holy Trinity when his mouth was so filthy with sin?
In a dramatic scene, an angel touches a coal to Isaiah’s lips, the very place he sensed his sin and guilt most. “Your guilt is taken away and your sin is atoned for.” How thorough is God’s forgiveness! Not only the sin itself, but the residual guilt is taken away. As only God can do it, Gospel salve is applied directly to the wound. Our Triune God heals us where we hurt.
Sensing his complete cleansing, Isaiah excitedly volunteers his mouth for noble purposes. Here is your chance to apply God’s Gospel salve to your own pet sins. God will heal you where you hurt. Then you can use your mouth to explain to others that the only thing more thorough than our natural corruption is Christ’s forgiveness.