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 is aware (knowing; realize) 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 (to look at quickly; a quick look) is one of the poisonous arrows of Satan. Many of such glances (to look at quickly; a quick look)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 (go into; go through; penetrate)) their eyes with burning rods. They will persist (continue firmly; refuse to stop or be changed) 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 (hug one another a hung) 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 (to look at quickly; a quick look) at a woman, but instantly looks away at the sky or turns his gaze down; before he could eliminate (get rid of, remove, omit) 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 (very great anger; rage) 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 (very many; several) traditions that denounce (condemn in public; express strong disapproval of) 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 (ripe, fully-grown or developed) 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 panic (unreasoning fear; fear spreading through a group of people so that they lose control of themselves) 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 (Keep in; hold in) only to those who commit fornication. The spouse (Husband and wife) 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)