Musannaf Ibn Abi Shayba 13:1823

Abu Bakr narrated to us, he said: Abu al-Ahwas narrated to us, from Simak, from Qabus ibn Mukhariq, from his father, who said: Muhammad ibn Abi Bakr was sent as a governor over Egypt. Muhammad wrote to Ali asking him about a Muslim who committed fornication with a Christian woman. Ali wrote: "Carry out the prescribed punishment (hadd) upon the Muslim who committed fornication with the Christian woman, and hand the Christian woman over to the Christians; let them judge regarding her as they wish."