surely Allah is Forgiving Merciful

This woman is not at all culprit of the crime."
Then Imam (a.s.) ordered for her release and she was released.
(Burhan - e - Quran)

Reasonable Precautions

Adultery is the root of degradation of society in the world and eternal punishment in the hereafter. Islam has therefore prescribed some obligatory rules for our protection. Allah, in His unsurpassed wisdom made these rules incumbent upon us. If these rules are obeyed, the Muslims can protect themselves from such a serious sin.

1.The Order for Hijab in the Quran

The Holy Quran has ordered women to cover themselves in some situations.
"And say to the believing women that they cast down their looks and guard their private parts and do not display their ornaments except what emerge thereof. And let them wear their head coverings over their bosoms, and not display their ornaments..." 
(Surah Nur 24:31)

It is also mentioned in Surah Ahzab, 
"O Prophet! Say to your wives and daughters and the women of the believers that they let down upon them their over garments, this will be more proper, that they may be known and thus they will not give trouble. And Allah is Forgiving, Merciful."
(Surah Ahzab 49:59)

In the same chapter, Allah says:
"O wives of the Prophet! You are not like any other of the women, if you will be on your guard, then be not soft in (your) speech, lest he whose heart has a disease yearn and speak a good word." 
(Surah Ahzab 49:32)

Another verse states, 
"And when you ask them (the wives of the Prophet) any goods, ask of them from behind a curtain, this is purer for your hearts and (for) their hearts." 
(Surah Ahzab 49:53)

In the above verses, the Muslim woman is ordered to veil herself. She must not come before namehram without Hijab. She should dress in such a manner that strange men do not get an opportunity to glance at those parts of her body which arouse passion; and thus make her an object of desire. It is the responsibility of a woman to assume such poise and behaviour that she does not excite a man's passions. Even a glance of lust can infatuate a man and a seemingly harmless encounter eventually lead to mischief and corruption in society, destroying entire families. In Iran, during the rule of the Shah when the law of Hijab had been revoked, the cases of fornication increased sharply. Every day many cases related to sexual crimes were heard in the courts of law. Every month many married mothers used to forsake their homes to enter into a perverse life of illicit sex. Five thousand such parents established a novel township outside the city of Tehran. The condition steadily deteriorated and came to a stage that every day approximately seven infants were found abandoned in the streets of Tehran, as reported by the commissioner. It is obvious that illicit children born as a result of fornication, whose parentage is not established, cannot create a position for themselves and are a burden to society. Due to the absence of Hijab, adultery and fornication became common and thousands of chaste women become immoral. One of the highly effective ways of protecting the society from the sin of adultery is that women wear hijab and ward off the evil glances of sensuous men.

2. Looking at the Namehram

The women are also ordered not to look at namehram men, and the men are similarly warned.

It is ordered in Surah Nur,
"Say to the believing men that they cast down their looks and guard their private parts; that is purer for them; surely Allah isaware of what they do."
(Surah Nur 24:30)

The Poisonous Arrow of Satan

It is narrated from Imam Ja'far as-Sadiq (a.s.):
"An evil glance is one of the poisonous arrows of Satan. Many of such glances becomes a cause of prolonged jealousy." 
(Wasaelush Shia)

Fornication of Organs

Both Imam Muhammad al-Baqir (a.s.) and Imam Ja'far as-Sadiq (a.s.) have informed,
"There is no man who is not to some extent guilty of fornication. The fornication of the eyes is the evil glance, the kiss is the fornication of lips and touching a namehram woman is the fornication of hands." 
(Wasaelush Shia)

It is also recorded that,
"Those who look at a namehram woman with an evil intention and fill their eyes with this sight (that is they look for a long time) Allah will, on the day of Qiyamat fill (pierce) their eyes with burning rods. They will continue in this way till Allah completes the hearing of the cases of all the people. Only after that will He order them to be thrown into Hell."
(Wasaelush Shia)

In the Chains of Fire with Iblees

That person who embraces a namehram woman will be tied with chains, together with Iblees on the day of Qiyamat. These chains shall be of fire and both of them shall be tossed into Hell together. The following are also the words of the tradition:
"One who glances at a woman, but instantly looks away at the sky or turns his gaze down; before he could remove his gaze fully, Allah marries him to a black-eyed houri and he creates such a freshness of belief in his heart that he is extremely delighted." 
(Wasaelush Shia)

It is reported from the Holy Prophet (s.a.w.s.) that he said;
"The wrath of Allah is very severe upon the married woman who apart from her husband sees another namehram man with a prolonged glance. When this woman does this, Allah the mighty invalidates all her good deeds and does not give her any rewards." 
(Behaarul Anwaar)

A few traditions mention that looking at a woman in hijab is also not allowed. Although it is a generally considered a makrooh act. Although there are numerous traditions that denounce glancing at namehrams these shall suffice for our purpose.

Alone in the Company of Namehram

It is Haraam for a stranger or namehram man to remain alone in company of a namehram woman when there is a risk of committing a sin, even though they may be busy in worship. In the same way women are ordered not to stay in company of namehram men when there is a chance of sinful act.

The Holy Prophet ( s.a.w.s.) says:
"One who believes in Allah and the Day of Judgement does not remain in a place where (even) the sound of breathing of the namehram women is perceived."

Imam Ja'far as-Sadiq (a.s.) said: 
"When the Prophet (a.s.) took allegiance from the women he told them to take an oath that they shall not sit alone in company of namehram men."
(Wasaelush Shia)

A lonely place means the one where there is no chance of anyone else entering or coming. Like a room, the door of which is locked from inside. Or a place not frequented by people.

Islam has prescribed severe penalty for a serious offence like adultery. Some of the aspects are given in the points mentioned below.

1) If a person commits an incestuous fornication he is to be killed according to Islamic laws.

2) If one sees that a stranger is fornicating with his wife, then he can kill both of them if he considers himself safe in doing so. But if he does not feel safe or if he does not wish to kill them, then apparently his wife is not prohibited for him.

3) If a Kafir commits adultery with a Muslim woman, he is to be killed according to shariat. Similarly, if a Muslim is punished thrice for fornication and is again proved guilty for the fourth time, he is to be executed.

4) If the person is sane, major, and legally married, and has a wife with whom he could establish sexual relation whenever he wants, and inspite of this he commits fornication with another sane, mature woman, he has to be stoned to death according to the Islamic law. And according to some Mujtahids, he must first be given a hundred lashes.

5) If a man does not fulfill the conditions listed in the above point, and if he commits fornication with a woman then his penalty according to Islamic law is a hundred lashes. Similarly, the married woman who willingly commits fornication should be stoned to death. If she is unmarried, then the penalty for her is a hundred lashes.

"As for the fornicatress and the fornicators, flog each other of them, (giving) a hundred lashes, and let not pity for them detain you in the matter of obedience to Allah, if you believe in Allah and the Last Day, and let a party of believers witness this chastisement." (Surah Nur 24:2)

After quoting the above ayat, the Journal of Anjuman-e-Tablighat-e-Islam writes:
Two points are derived from this. The first is that the punishment of the adulterer is carried out in the presence of other people. This will be a warning and a lesson to them. They will be terrified of committing the same sin after witnessing the horror of the punishment.

Another point, although its truth is not established, is that the punishment acts as a cure for the diseases of the sinner. It could be that due to the hundred lashes, the bodies of the sinners are so much heated that the germs that have entered their bodies are annihilated before they could multiply and spread.

One more point to be noted is that the germs of disease like syphilis etc. are not confined only to those who commit fornication. The spouse of the fornicator may also contract these diseases. Marriage with an adulterer is therefore detestable and is discouraged. If an adulterer man marries an adulteress woman, an innocent person is not victimised, but their deeds will definitely affect their progeny adversely. Their future generations will be contaminated with the evil of their sin and there will be some deformity or the other in their progeny. It is for this very fact that the religion of Islam says;
"The fornicator shall not marry any but a fornicatress or idolatress, and (as for) the fornicatress, none shall marry her but a fornicator or an idolater; and it is forbidden to the believer." 
(Surah Nur 24:3)

When Adultery is Proved According to Shariat

It must be clarified that the penalty for adultery could be imposed when the sin is proved from the viewpoint of Shariat. As it has been stated earlier, adultery is only proved if the conditions necessary for it are fulfilled. One of the conditions is that all the four just witnesses should testify unanimously as to the time and place of the crime. They must also know the woman by sight. Otherwise, there arises the possibility that the person who performed the sexual act with the woman may have been her husband.