Musnad Ahmad 1012:114

Abdullah narrated to us, Shayban ibn Abi Shaybah narrated to us, Jarir ibn Hazim narrated to us, al-Hasan narrated, saying: Ubadah ibn al-Samit said: "The verse {And those who commit unlawful sexual intercourse of your women} [An-Nisa: 15] until the end of the verse was revealed to the Messenger of Allah, peace and blessings of Allah be upon him. He said: So the Messenger of Allah, peace and blessings of Allah be upon him, acted upon that regarding them. While the Messenger of Allah, peace and blessings of Allah be upon him, was sitting and we were around him—and it was such that when the revelation descended upon him, he would turn away from us and we would turn away from him, and his face would darken and he would be distressed by that—when the revelation was lifted from him, he said: 'Take from me.' We said: 'Yes, O Messenger of Allah.' He said: 'Allah has made a way for them: the unmarried with the unmarried, one hundred lashes and banishment for a year; and the married with the married, one hundred lashes, then stoning.'" Al-Hasan said: I do not know if it is from the hadith or not: "If they testify that they were found under a blanket—they do not testify to the act of intercourse—he is lashed one hundred times, and their heads are shaved."