Read: John 8:1-11
Then neither do I condemn you, Jesus declared. Go now and leave your life of sin. (John 8:11b)
In this passage, a woman caught in adultery was brought by the church leaders to Jesus. I do not know if we can accurately picture what was going on when this woman was brought before Jesus. I can see her being dragged in, red faced, her hair in disarray. She is angry, upset, rebellious, and bitter, perhaps striking out against her accusers. But when she sees how Jesus handles this crowd of hypocritical judges, and feels that his sympathies are with her, somewhere the mercy and love that was in his face and voice began to touch her. She realized how wrong she was, that she had sinned, and she repented. When she did, Jesus forgave her, obviously anticipating his death upon the cross for her.
The cross is always an eternal event in the mind of God. The sins of the people who lived in Old Testament days were also forgiven on the basis of the death of Jesus on the cross. There is no other way that God can forgive sin. In anticipation of that cross, Jesus forgave her sin. The proof of it is in the words he said, Go, and do not sin again.