Musnad Ahmad 830:64

'Abd al-Samad narrated to us, Zakariyya ibn Sulaym al-Minqari narrated to us, he said: I heard a man narrating to 'Amr ibn 'Uthman, and I was a witness, that he heard 'Abd al-Rahman ibn Abi Bakrah narrating that Abu Bakrah narrated to them that he witnessed the Messenger of Allah (peace and blessings of Allah be upon him) upon his mule, standing, when they brought a pregnant woman. He said: "She has committed adultery," or "She has committed fornication, so stone her." The Messenger of Allah (peace and blessings of Allah be upon him) said to him: "Cover yourself with the covering of Allah." So she went back. Then she came a second time, and the Prophet (peace and blessings of Allah be upon him) was upon his mule, and he said: "Stone her, O Prophet of Allah." He said: "Cover yourself with the covering of Allah." So she went back. Then she came a third time, and he was standing until she took hold of the bridle of his mule and said: "I adjure you by Allah, will you not stone her?" He said: "Go until you give birth." So she went and gave birth to a boy. Then she came and spoke to the Messenger of Allah (peace and blessings of Allah be upon him), and he said to her: "Go and purify yourself from the blood." So she went, then she came to the Prophet (peace and blessings of Allah be upon him) and said: "She has purified herself." The Messenger of Allah (peace and blessings of Allah be upon him) sent women and ordered them to examine the woman. They came and testified to the Messenger of Allah (peace and blessings of Allah be upon him) of her purity. He ordered a pit to be dug for her up to her chest. Then the Messenger of Allah (peace and blessings of Allah be upon him) and the Muslims came. The Prophet (peace and blessings of Allah be upon him) took a pebble the size of a chickpea and threw it. Then the Messenger of Allah (peace and blessings of Allah be upon him) turned away and said to the Muslims: "Stone her, and beware of her face." When she had expired, he ordered her to be taken out, and he prayed over her. Then he said: "If her reward were divided among the people of the Hijaz, it would suffice them."