This requires the Muslim, whether male or female, to know the ruling of Islamic sacred law in order that he/she may follow it and be among those who Allah describes “The saying of (all true) believers when they appeal unto Allah and His messenger to judge between them is only that they say: We hear and we obey. And such are the successful.” (Surah al-Nur: 51)

Islamic sacred law seeks to protect people from shameful deeds just as it seeks to prevent them.  Islam is a complete way of life, and it seeks to grant individuals a lifestyle distinguished in cleanliness and purity. In this regard, Islam not only prohibits the sin, but it prevents paths leading to the sin as well.   That is why Islam prohibited all shameful deeds, whether they are open or secret.  Perhaps one will not find any aspect that Muslims have been commanded to be cautious of as they did when it comes to gender relations.  That is because there is a strong innate desire in the self for it. Hence, one needs to struggle against his/her self and keep mindful of Allah on one hand, and on the other hand he/she needs self restraint along with many laws that will prevent him/her from the sin.  

We are commanded to lower our gaze, not be in seclusion with the other gender, or mingle with them without necessity, openly showing beauty, and also shaking hands with women who one could marry.  Allah says “Say to the believing men to lower their gaze and protect their private parts, that is more pure for them, verily Allah is well aware of what they do” (Surah al-Nur: 30)

Abudullah ibn Mas`ud said: The Prophet (peace and blessings be upon him) said: “The woman is an awrah (must be covered) if she leaves the devil accompanies her.  

The author of al-Adwa’ (An explanation of the Qur'an) said: The women is all an awrah and is required to cover.  The command to lower the gaze was out of fear of falling into trials, and there is no doubt that physical contact is a stronger temptation than looking with the eye and everyone knows that.

Imam Nawawi said: Our companions (the scholars of the Shafi' Madhab in Fiqh) have said that everything which is prohibited to look at is also prohibited to touch, nay touching is even worse.  The Prophet (peace and blessings be upon him) prohibited everything that leads to sin, like his prohibiting men from entering upon women or being in seclusion with them by his saying “Be very careful not to enter upon women”.

There is no difference of opinion among scholars that it is prohibited to shake hands with a woman out of desire. This also applies to hugging, or touching any other part of her body.  The Prophet (peace and blessings be upon him) considered this a form of fornication.  The Prophet (peace and blessings be upon him) said: The son of Adam’s portion of fornication has been written on him, and he will do it without a doubt.  Gazing is the fornication of the eyes, hearing is the fornication of the ears, speech is the fornication of the tongue, touching is the fornication of the hand, the heart aspires and wishes, and the private part either allows it to take place or doesn’t. (Sahih Al-Bukhari) 

There is also no disagreement that one can shake hands of women who he can’t marry (such as his mom or sister) because in such a case there is no desire, and if -God forbid- there is some kind of desire, in this case any kind of physical contact will also be prohibited.  

The primary evidence in Islamic sacred law indicating the prohibition of handshaking with the opposite gender is the concept of "Forbidding acts which lead to greater harm" (Saddu Tharee'a). This concept is supported by numerous evidences. Basically, this concept entails that everything which usually leads to a prohibition is also prohibited. If the Qur'an clearly mentions that lowering the gaze is mandatory, then that implicates the prohibition of physical contact and shaking hands between opposite genders.

The Prophet (saws) said, "It is better for one of you to be stabbed with a metal needle than to touch a woman who is not Halaal for him". In addition, the Prophet (saws) would never shake the hand of a female who is not related to him. In Sahih Bukhari it states that Aisha quoted: "Allah's Apostle used to test them (women) according to this Verse: "O you who believe! When the believing women come to you, as emigrants test them . . . for Allah is Oft-Forgiving, Most Merciful." (60:10-12) Aisha said, "When any of them agreed to that condition Allah's Apostle would say to her, 'I have accepted your pledge of allegiance.' He would only say that, but, by Allah he never touched the hand of any women (i.e. never shook hands with them) while taking the pledge of allegiance and he never took their pledge of allegiance except by his words (only)."

In another narration, the Prophet (saws) said to a group of women prepared to give him their allegiance, "I do not shake the hands of women. What I say to a hundred women, is the same as what I say to one woman".   

The Prophet (saws) is the one safeguarded from sin and he is a guardian over all women. He is like their father as we can understand from the verse: The Prophet is more entitled to the (obedience of the) believers than (they are entitled to) their own selves" (Al-Ahzaab: 6) If it is permissible to shake the hands of marriageable individuals, it would have been permissible for him to do so as he was taking their pledge of allegiance. Thus, shaking hands in other situations should be more clearly understood as prohibited.

Imam Nawawi said in his explanation of the hadeeth reported by Aishah (raa), "This Hadeeth indicates that the pledge of allegiance is performed orally by women, without taking their hands. But for men, there is hand contact made in the process."  

One female companion related: "A group of women and I came to the Prophet (saws) to pledge our allegiance. We said: O Prophet of Allah, we pledge that we will not associate any partners with Allah, nor shall we steal, fornicate, murder our children or utter slander, intentionally forging falsehood (i.e. by falsely claiming children to belong to their husbands), and we will not disobey you in performing any good act. Then, the Prophet (saws) said: "You will do so to the best of your ability". We responded: "Allah and His Prophet or more merciful with us than we are with our own selves. Allow us to give you our pledge of allegiance O Prophet of Allah". The Prophet Responded: "I do not shake hands with women. My speech to a hundred women is like my speech to one woman."

As he was explaining handshaking to be a Sunnah (an act religiously recommended), Imam Ibn Hajar mentioned: "Shaking hands with a foreign woman (not a wife, sister or etc.) is an exception to the general rule (in Islamic sacred law) encouraging the performance of this act".

When A'ishah Al'uthriyya visited Al-Hasan, the grandson of the Prophet, he welcomed her and said: "If it wasn't that the Prophet of Allah prohibited handshaking with women, I would have shaken your hand".

Upon researching the views of our scholars, you will find that some have been very lax on this issue, while others have taken a very harsh position. But you will find others who were more moderate, and –Allah knows best- this is closest to truth. Reason being, the textual evidences used can be interpreted in other ways, and some scholars have regarded some of these narrations to be inauthentic. Furthermore, some of these narrations which use the word "touch" can be understood to implicate things beyond merely a handshake.

However, after carefully studying this issue you can come to the conclusion that there is consensus amongst our scholars that handshaking is prohibited in cases which lust is involved or greater harm is expected. As for handshaking in general –whether or not there is lust- most of the scholars regard it to be prohibited as well.

Ibn Muflih mentioned: Shaikh Taqiiyuddeen –ibn Taymiyyah- views it to be prohibited based on the fact that hand contact is more severe than gazing (and we've been commanded to lower our gaze)".  

Shaikh Saeed Ramadan Al-Buti said: I do not of any difference of opinion about physical contact of a man with a woman foreign to him being prohibited".

The grand scholar Muhammad Al-Ameen Ash-Shinqeeti mentioned: "Know that it is not permissible for a foreign man to handshake with a woman foreign to him, nor may any part of his body touch any part of her body."

The reason why handshaking is prohibited is because it opens the doors for lust to be aroused in both individuals. If glancing at the other gender from a distance can arouse lust, how about actual physical contact?!

By way of prohibiting handshaking, Islam wants to develop a sense of cautiousness in both genders. Islam wants both genders to display their chastity! Islam wants them to internalize modesty! It aims to block the path of Shaytan! Shaytan encourages both sides to speak and joke with one another and, in turn, leads them to greater and more harmful practices which are quite prevalent especially between co-workers and students.

Important clarifications:

The prohibition of handshaking is based on the concept of "Forbidding acts which lead to greater harm" (Saddu Tharee'a). Thus, the cause of prohibition is not the act of handshaking in itself, but rather external factors that were involved in the act. Hence, it is from the minor sins, not the major sins. The same reasoning applies to gazing at the opposite gender.

Furthermore, acts that have been prohibited due to external factors can be allowed in a case which there is a need. Consequently, the scholars have made exceptions to the general rule. So, the doctor can touch an ill woman for the sake of treatment. Handshaking with an old woman who is not likely to get married and there is no fear of a greater harm is permissible. Likewise, handshaking with an old man who no longer lusts women is allowed. The same would apply to any situation in which there is no fitna (fear of lust or greater harm) existing.

In the West, people do not know about Islam itself, let alone this ruling on handshaking. This reality makes it mandatory for Muslims to announce to people their faith and culture. They must point out the wisdoms and the reasoning of Islamic sacred law behind rulings such as this one.

In a situation where a woman (or vice versa) who does not know of this ruling or even of Islam extends her arm and you shook hands with her, then you have not fallen into sin In Sha'llah. Reason being I wouldn't want you turning down his/her handshake to lead to a greater harm. I wouldn't want it to spark a negative reaction towards their view of Islam, or even lead them to feel emotionally hurt. This is what ought to be kept in mind based on "Fiqhul Muwaazana" (the Fiqh of measuring circumstances and their results). But at the same time, the Muslim must do his/her part in explaining to people the principles of Islam before situations such as these occur.

In addition, it can be said that handshaking in college or job interviews would be permissible. I say so from the perspective of regarding the culture of the people in America who generally view handshaking and making eye contact during a dialogue to be very significant issues of character. In addition, college and job interviews are a necessity, and formal meetings such as these eliminate the fear of fitna. Since these are necessities, then we can apply the concept which states: Acts that have been prohibited due to external factors can be allowed in a case which there is a need.

Furthermore, I use in support of my reasoning the narration which mentions that a young girl grabbed the hand of the Prophet (saws) and took him to the outskirts of Madinah so he may help her in something she needed. Also, another narration mentions that Umar ibn Al-Khattab placed his hand on the shoulder of an old woman as she was asking him a question. Thus, it is okay to handshake with someone whom there exists no fitna with. Allah knows best.