A man in a Jewish town conceived an intention to commit adultery. He approached a woman who was not his wife and arranged to meet her secretly at a set hour in a set place. The Exempla preserves the story without naming him, because the story could be told about anyone.
The woman he had approached went to his wife. She explained what the husband had planned. Together, the two women devised a quiet answer to his invitation. That night, when the man came to the arranged meeting place, the woman who arrived was his wife. She was veiled. She did not speak. He did not recognize her.
The encounter took place. He believed he had broken his marriage. He rode home the next morning burdened with guilt, the heaviness of a man who has crossed a line he cannot uncross. Over the days that followed he began the slow work of teshuvah, repentance. He could not undo what he had done, but he could begin to become a man who would not do it again.
At last he confessed to his wife. He told her that he had sinned with another woman, and he asked how he could ever make it right. His wife looked at him and delivered the line that has traveled through the Jewish moral tradition. "You drank from your own cup."
The man had intended adultery, and adultery in his heart had been committed. The rabbis preserve the story to show how seriously the tradition takes the gap between intent and act. The cup his hand reached for was a cup he was not permitted to lift, even though the wine inside it was his own. The lesson is that the wrong lies not only in the drink, but in the reach.