Sayyiduna Abu Waqid al-Laythi (may Allah be pleased with him) said that a man came to Sayyiduna Umar (may Allah be pleased with him) in Syria and said that he had seen another man with his wife. So Sayyiduna Umar (may Allah be pleased with him) sent Sayyiduna Abu Waqid (may Allah be pleased with him) to his wife to verify it, and he came to his wife. There were women around her. Sayyiduna Abu Waqid (may Allah be pleased with him) told her the whole matter and said that she would not be punished on his word, and Sayyiduna Abu Waqid (may Allah be pleased with him) began prompting her to deny it, but she refused to deny it and confessed. So by the order of Sayyiduna Umar (may Allah be pleased with him) she was stoned.
Imam al-Shafi'i (may Allah have mercy on him) said that when Sayyiduna Umar and Sayyiduna Uthman (may Allah be pleased with them both) had a woman stoned, they did not say that they themselves would be present.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحدود / 16960