Jami` at-Tirmidhi 1441

Narrated Abu 'Abdur-Rahman As-Sulami:"Ali gave a Khutbah, and said: 'O people, establish the penalties upon your slaves, those married from them and those unmarried. A slave girl of the Prophet (ﷺ) committed illegal sexual intercourse so he ordered me to whip her. I went to her and she was just experiencing her post-natal bleeding, so I feared that if I were to whip her I would kill her' - or he said: 'She would die' - 'so I went to the Messenger of Allah (ﷺ) and I told that to him. So he said: 'You did well