In a small Jewish village in the Ukraine, a young man became angry with the rabbi. In his anger, he shared a lie with one friend, speaking evil of the rabbi. As is typical, particularly in a small town, the one man told another, who told his wife, who told her sister, and eventually the rabbi himself heard the story. The rabbi was deeply hurt by the lies being told; but could do nothing to counter the now widespread story.
After a few weeks, the young man realized he had been wrong to be angry at the rabbi, and even more wrong to have told the story about the rabbi. With a truly repentant heart, he went to the rabbi and confessed both his anger and the lie he had told. He offered to do anything to repair the damage he had done. The rabbi offered the young man one simple task. The young man was overjoyed and gladly asked what he must do. The rabbi told him to go home and get a feather pillow, take it to the center of town on a windy day, and cut it open. Once all the feathers had been scattered by the wind, he told the young man to simply walk around and gather up each and every feather and return it to the pillow case.
The young man's countenance dropped, and he told the rabbi that such an assignment was impossible. The rabbi shook his head and told the young man that just as it was impossible to regather the feathers, so it was impossible to regather the lie he had spread. The Rabbi could and would forgive the young man, but the damage could never be completely undone.
(Whenever you speak evil of another, three people are hurt. First, the person you are speaking about is hurt. Second, you hurt yourself when you speak evil about another. You pollute your own thoughts by focusing on the evil, and you also tarnish your image, as people come to know you as one who spreads a bad report--a gossip. Third, you hurt the person you tell. You pollute their mind and their image of the other person, and you tempt them to continue the gossip train and share this same evil report with others. Remember, all three people are damaged, even if the evil report is true!)
The rabbis teach that the only time it is permissible to share an evil truth, or we might say "bad report," about someone is when not doing so will cause damage to the person you might tell.
Story taken from BRIDGES FOR PEACE Israel Teaching Letter titled GUARD YOUR TONGUE.