Suppose someone were to come up to you and punch you in the nose. And suppose in an act of compassion you were to say to that person, “I forgive you.” And suppose they responded, “There’s no need for you to forgive me. I’ve already forgiven myself.” Friend, listen to me. Only the punchee can forgive the puncher. Sin is a clenched fist in the face of God, and only God can forgive sin.
What was the reason for the cross? I can give it to you in one word, and that word is sin. “For Christ also hath once suffered for sins, the just for the unjust, that He might bring us to God, being put to death in the flesh, but quickened by the Spirit” (1 Peter 3:18).
There’s enough Gospel dynamite in that one verse to blow the sin, the hatred, the sorrow, the sickness out of anybody’s life, but that dynamite must be ignited by the spark of faith.