Under Muslim law, adultery (extramarital sex in general) is sexual intercourse by a married person (whether man or woman) with someone to whom they are not married. Adultery is a violation of the marital contract and one of the major sins and is condemned by God in the Qur’an. Zina means consensual premarital sex.
Qur’anic verses prohibiting adultery include:
“Do not go near to adultery. Surely it is a shameful deed and evil, opening roads (to other evils)” (Quran 17:32).
“Say, 'Verily, my Lord has prohibited the shameful deeds, be it open or secret, sins and trespasses against the truth and reason”’ (Quran 7:33).
“Women impure are for men impure, and men impure are for women impure and women of purity are for men of purity, and men of purity are for women of purity.” (Quran 24:26)
Though strict Muslim law prescribes severe punishments for extramarital sex, by both men and women (premarital sex is punishable with up to 100 lashes, while adultery is punishable by stoning), to obtain conviction of zina[consensual premarital sex], the act of sexual penetration must be attested by at least four male Muslim witnesses of good character, with the accused having a right to testify and their testimony given the most weight in the eyes of the judge(s). Also, punishments are reserved to the legal authorities and false accusations are to be punished severely.[23][24] It has been said that these legal procedural requirements were instituted to make it impossible to obtain conviction.[25] (It should be noted that the above punishment of stoning is never given in the Quran but only in the Hadith. The only punishment for adultery given in the Quran is one hundred lashes and restriction of future marriage to another adulterer or the partner in the act).
Conditions for adultery:
The accused, before the accusation, must be known as a practising Muslim.
The accused must possess common sense. The accused must not have been in an intoxicated state of mind while the act was committed.
The accused must be an adult.
The accused must have committed adultery of his/her own free will.
There must be four male witnesses (or pieces of evidence) to support the accusation (of sexual penetration).
A hadith confirms this:
Reported by many companions that Ma’iz went before Muhammad in the Mosque and said, “I have committed adultery, please purify me.” (In another report, Muhammad asked Ma’iz that the reports he heard about him are correct or not[5]) Muhammad turned his face away from him and said “Woe to you, go back and pray to Allah for forgiveness.” But the boy again came in front of Muhammad and repeated his desire for purification. The act was repeated three times, until Abu Bakr, sitting close by, told the Ma’iz to leave, as the fourth repetition of the plea would get him stoned. But the man persisted. Muhammad then turned to him and said “you might have kissed or caressed her or you might have looked at her with lust (and so assumed that you committed Zina)”. Ma’iz replied in the negative. Allah’s Apostle said “did you lie in bed with her?” Ma’iz replied in the affirmative. He then asked, “did you have sexual intercourse?” Ma’iz replied in the affirmative. Then Muhammad got quite uncomfortable, and asked “Did your male organ disappear in the female part?” Ma’iz replied in the affirmative. He then asked, once more, whether Ma’iz knew what Zina means. Ma’iz replied “yes, I have committed the same act a husband commits with his wife.” Muhammad asked if he was married, and he replied “yes”. Muhammad asked if he took any wine, and Ma’iz again replied in the negative. Muhammad then sent for an inquiry from the neighbors of Ma’iz, whether or not Ma’iz suffered from insanity. The replies all came in the negative. Muhammad then said, “had you kept it a secret, it would have been better for you.” Muhammad then ordered Ma’iz to be stoned to death. During the stoning, Ma’iz cried out, “O people, take me back to the Holy Prophet, the people of my clan deluded me.” When this was reported to Muhammad, he replied “Why did you not let him off, he might have repented, and Allah may have accepted it.”
Sources:
en.wikipedia.org/wiki/Adultery#Islam
en.wikipedia.org/wiki/Zina_(Arabic
Ah, so there’s no witnesses to Mohammed’s act, so it’s not adultery. I guess his wives didn’t know what he was doing, since they were surprised by what he had done. Ah well, such is the law of Allah.