Hadith 21: The Condition of Honor

Imam Sadiq (as) said: Whoever wants to be in the neighborhood of the Prophet (pbuh&HP) and next to Ali (AS) and Fatima (AS) should not leave the pilgrimage of Imam Hussain (AS).  
Wasa'il al-Shi'ah, vol. 10, p. 331, p. 39

Hadith 22: Pilgrimage, Divine Duty

Imam Sadiq (as) said: If one of you observes the Ihram of Hajj for the entire of his life but does not visit Imam Hussain (as), he has left the right of the Messenger of Allah (PBUH&HP) because the right of Hussain (as) is a divine duty and obligatory for every Muslim.
 Wasa'il al-Shi'ah, vol. 10, p. 333

Hadith 23: Karbala, the Kaaba of Perfection

Imam Sadiq (as) said: Whoever does not visit the grave of Imam Hussain (as) until he dies, his faith will be incomplete and his religion will be incomplete, and when he goes to heaven, he will be lower than the believers there. 
Wasa'il al-Shi'ah, vol. 10, p. .335

Hadith 24: From Pilgrimage to Martyrdom

Imam Sadiq (as) said: Do not leave the pilgrimage of Imam Hussain (as) and recommend it to your friends and companions as well! May Allah prolong your life, increase your sustenance, and may Allah bless you alive and you will not die except as a martyr. 
Wasa'il al-Shi'ah  vol. 10, p. 335

Hadith 25: The Hadith of Love

It was narrated from Imam Sadiq (as) that he said: Whoever Allah wants good, will put the love of Hussain (AS) and his pilgrimage in his heart, and whoever Allah wants bad, will have him hate Hussain (AS) and anxious with his pilgrimage.
 Wasa'il al-Shi'ah  vol. 10, p. 388, Sea of Lights, vol. 98, p. 76

Hadith 26: A Sign of Being a Shiite

Imam Sadiq (as) said: Whoever does not visit the grave of Imam Hussain and dies as our Shiite and dies, is not our Shiite, and even if he is from the people of Paradise, he is the guest of the people of Paradise.
Kamel Al-Ziyarat, p. 193, Bihar Al-Anwar, vol. 98, p.4

Hadith 27: Ascension Platform

Imam Sadiq (as) said: Whoever visits the grave of Hussain (as) and has knowledge of the right of that Imam, Allah Almighty will register him in the highest rank.
Man la yahzurul Faqih, vol. 2, p.581

Hadith 28: The School of Knowledge

Imam Musa Kadhim (as) said: The least reward that is given to the pilgrim of Imam Hussain (as) on the banks of the Euphrates is that all his sins, before and after, are forgiven. Provided that he knows the right, honor and guardianship of that Imam.
Mustadrak al-Wasa'il, vol. 10, p. 236, quoting Kamil al-Ziyarat, p. 138

Hadith 29: Like the Pilgrimage of Allah

Imam Reza (as) said: Whoever visits the grave of Imam Hussain (as) on the banks of the Euphrates is like the one who has visited Allah. 
Mustadrak al-Wasa'il, vol. 10, p. 250, quoting in full

Chapter Three: Ashura and Arbaeen

Hadith 30: Pilgrimage at Ashura

Imam Sadiq (as) said: Whoever visits Imam Hussain (as) on the day of Ashura, heaven will be obligatory for him. 
Iqbal al-A'mal, p. 568

Hadith 31: Above Prosperity

Imam Sadiq (as) said: Whoever wakes up on the night of Ashura next to the shrine of Imam Hussain (as), on the Day of Judgment he will rush to Allah stained in his blood, like someone who was killed in Karbala next to Imam Hussain (as). 
Wasaelu shiah, vol. 10, p.372

Hadith 32: Signs of Faith

Imam Hassan Askari (as) said: The signs of a believer are five: 

1 Fifty prayers 

2 Arbaeen pilgrimage

3 Ring in the right hand 

4 Prostrating on the ground 

5 Saying loudly the name of Allah, (Bismillah Rahman Rahim)

 Wasaelu shia, vol. 10, p. 373, and also Al-Tahdhib, vol. 6, p. 52

Chapter Four: Torbat and Tasbih of Love

Hadith 33: His Porch 

The Prophet of Islam (PBUH&HP) said: Know that the answer to prayer is under the dome of his shrine and healing is in his soil, and the Imams (as) are of his children.
 Mustadrak al-Wasa'il, vol. 10, p.335

Hadith 34: Soil and Training

Imam Sadiq (as) said: Take your children with the soil of Hussain (as) (Karbala) because the soil of Karbala insures your children. 
Wasaelu Shiah, vol. 10, p.410

Hadith 35: The Greatest Medicine

Imam Sadiq (as) said: The cure for any pain is in the soil (torbat) of Hussain (as) and it is the greatest medicine. Kamil Al-Ziyarat, p. 275 and Wasa'il al-Shi'ah, vol. 10, p. 410

Hadith 36: Torbat (soil of Karbala) and seven hijabs

Imam Sadiq (as) said: Prostration on the soil of Hussain (as) tears the seven veils. 
Mesbah al-Muttahid, p. 511, and Bihar al-Anwar, vol. 98, p. 135

Hadith 37: Prostration on the Soil of Love

Imam Sadiq (as) did not prostrate on the ground except on the soil of Hussain (as) and he did this in violence for the sake of Allah.
Wasailu shiah vol. 3, p.608

Hadith 38: Rosary with the Soil of Karbala

Imam Sadiq (as) said: Prostration on the soil of Karbala can light up to the seventh earth, and whoever has a rosary from the soil of the shrine of Hussain (as) with him, is a truthful person, even if he says nothing.
Man la yahzurulFaqih vol 1 p 268 

Hadith 39: Healing Soil

Imam Kadhim (as) while narrating a hadith announcing his death, said: do not take anything from the soil of my grave to seek blessings, because it is forbidden for us to eat any soil except the soil of my grandfather Hussain (as), Allah Almighty has healed only the soil of Karbala for the Shiites and our friends. 
Jami ahadith, vol. 12, p.533

Hadith 40: One of the Four Needs

Imam Musa ibn Ja'far (as) said: Our needs are four things:

1. Prayer mat on which prayers are offered.

2. Rings on the finger

3. Toothbrush with which to brush teeth

4. A rosary from the shrine of Imam Hussain (as) Tahdhib al-Ahkam, vol. 6, p. 75
 

Imagine one of your ordinary days in which you go out in the morning to go to work or the university or anywhere else. You attend some gatherings. You see men and women around you interacting and greeting on different occasions and in various manners, more frequently shaking hands.

You are a member of this community too, and you also used to greet different people with whom you had interactions every day and perhaps it was not important for you if the person you shake hands with is a man or a woman. But now, as a Muslim, you must know that shaking hands in Islam with the opposite gender is forbidden. If this has raised a question in your mind, we will be discussing the issue here.

Psychological Views on Shaking Hands

As a scientific fact, everything we do, or we say, or any other kind of action we perform via every part of our body from legs up to the eyes, or even any thought passing into our minds has energy in itself. Once we bring something into existence, such as an utterance or an action, hence its specific kind of energy, it will never go to an end; but it is transformed and transferred to different targets, leaving its influence on them and first on ourselves.

Thus in our interactions, we are producing some kind of energy. So when people from the opposite genders confront each other and shake hands or kiss or hug each other, as a kind of greeting, what kind of energy is being interchanged between them?  

The Main Reason Behind the Prohibition of Shaking Hands in Islam

God has put some kind of desire in human’s nature by which the opposite sexes are attracted to each other. When women and men who are non-Mahrams, greet each other in any way involving touching their bodies or looking at one another in such a way that arises this desire, they will be leaving a negative effect on each other; although it may feel pleasant.

Once this instinct is provoked, to satisfy their sensual needs, people may go further in their relationships and may be driven into immoral and sinful acts. The final result would be regret, distrust among people and broken families and other mental and physical consequences. Because in Islam’s viewpoint, sensual desires must only be satisfied among spouses. Due to this and some other reasons we might not know, God has set some rules regarding the quality of relationships between women and men. Following these rules will make concepts like marriage and family meaningful.

We Can Control Ourselves

One might say that we do not have any bad intentions in our relationships with those who are considered non-Mahram for us. We can control our desires when confronting them and nothing sinful happens. But the prophet Mohammad (PBUH) and his family who were the purest ones of all time obeyed these rules too.

They avoided any kind of interaction with non-Mahrams that are considered to be Haram. 
When people came to the prophet for Bay’ah (to swear allegiance), he shook hands with men, and for women, a container of water was brought in which the prophet put his hand and took his hand out and then women put their hands in the water to make their pledge [2]. 

The Islamic Etiquette of Touching, Looking and Talking

A Muslim is only allowed to touch the body of those of the same gender and those of the opposite gender who are Mahram for him/her.
A man can only look at the face and hands of a non-mahram woman if they do not have decorations and on the condition that it is not for pleasure [i]. 

In the Quran, we read: “Say to the believers, that they cast down their eyes and guard their private parts… And say to the believing women, that they cast down their eyes and guard their private parts, and reveal not their adornment, save such as is outward…” (24:30-31). Non-Mahrams must be careful with their speaking, too. In another part of Quran, we read: “…be not abject in your speech, so that he in whose heart is sickness may be lustful, but speak honorable words.” (33:32). In these verses of the Holy Quran, the danger of arousing sexual desires through speaking and looking has been warned. However, there are no limits to touching, looking, and talking between spouses.

And some exceptions may occur. For example, if a doctor of the same gender is not available, one can go to a doctor from the opposite gender and touching and looking is permitted in this case. But only in case of necessity and as much as needed.

How to Avoid Shaking Hands in Islam with Non-mahrams

Most probably it will be hard for you to find an excuse to refuse to shake hands with non-mahrams especially those with whom you had usual interactions before. Because in your society this may result in a misunderstanding about your attitude toward people.

When a non-mahram wants to shake a hand with you, if you politely say that due to religious matters you can't shake hands but you are pleased to meet them, in most cases, they will accept it from you without being offended. This would be better rather than falsely mentioning illness and other things. But if you explained your reason honestly and someone reacted badly, you do not need to bother yourself convincing that person.

To conclude, shaking hands, kissing, hugging, and every other kind of greeting and interaction between non-Mahrams which involves touching and also looking at each other on purpose, and talking with each other in a tempting manner are Haram in Islam.

Notes:
[i] Refer to the article “The Islamic etiquette of looking” for more information.                     

References: 

1. shakin hands in islam
2. Mohammad ibn Jarir Tabari, “Tarikh-e Tabari,” vol.3, p.61-62.