"Also (forbidden are) women already married, except those whom your right hands possess. Thus has Allah ordained for you. All others are lawful, provided you seek them from your property, desiring chastity, not fornication. So with those among them whom you have enjoyed, give them their required due, but if you agree mutually after the requirement (has been determined), there is no sin on you. Surely, Allah is Ever All-Knowing, All-Wise." - Quran 4:24 (read more)

"Narrated 'Abdullah bin 'Umar : The Jew brought to the Prophet a man and a woman from amongst them who have committed (adultery) illegal sexual intercourse. He ordered both of them to be stoned (to death), near the place of offering the funeral prayers beside the mosque." - Sahih Bukhari 7:62:64 (read more)

"The Prophet -- the blessing and peace of Allah be upon him -- said, "He who changes his religion must be killed"; this holds true both for men and women. The apostasy of a man calls for putting him to death. It is unanimously agreed upon that apostasy is a horrible crime deserving a horrible punishment. The apostasy of a woman is no less horrible. Therefore, it too deserves a corresponding punishment: death." - Abdurrahmani'l-Djaziri