Maysarah said: A mother and her son came to Sayyiduna Ali (may Allah be pleased with him). She said: He has killed my husband. The son said: My slave had intercourse with my mother. Sayyiduna Ali (may Allah be pleased with him) said: You have both come to ruin. If you are truthful, we will kill him; and if your son is truthful, we will stone you. Then Sayyiduna Ali (may Allah be pleased with him) went to the prayer, and the boy said to his mother: What do you think, that I should be killed or that you should be stoned? So the two of them left. When he (may Allah be pleased with him) finished the prayer and asked about them, he was told that they had gone.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأشربة والحد فيها / 17615