The Cambridge dictionary defines wisdom as using knowledge and experience to make good decisions and judgments. (1) The most similar equivalent for this word in Arabic is the word  “حکمة” (“Hikmah”) which denotes justice, knowledge and tolerance. (2) 

This word has been used so many times in the holy Quran and has a special meaning in  Islamic literature. The holy Quran says:
Allah grants wisdom to whomever He wishes, and he, who is given wisdom, is certainly given an abundant good, and none takes admonition except those who possess intellect. (2:269) 
About this verse of the Quran, Imam Sadiq (AS) says:
(In this verse) Allah The Almighty has portrayed the intellectuals in the best way. (3)

Hikmah is the message of the Prophets

Allah The Almighty has rapidly pointed out this fact that He has sent the prophets with “Hikmah” and they should teach people how to be wise. The holy Quran says:

Allah certainly favored the faithful when He raised up among them an apostle from among themselves to recite to them His signs (the verses of Quran) and to purify them and teach them the Book and wisdom, and earlier they had indeed been in manifest error. (3:164)
And:
There have already come to them, reports (via the Prophets) containing admonishment, [and representing] far-reaching wisdom; but warnings are of no avail! (4:54)
Also: 
Invite to the way of your Lord with wisdom and good advice and dispute with them in a manner which is the best manner.. (16:125)
And: 
When Jesus brought those manifest proofs, he said, ‘I have certainly brought you wisdom, and [I have come] to make clear to you some of the things that you differ about, so be wary of Allah and obey me. (43:63)

Allah almighty even says that the holy Quran is a book full of wisdom:
These are among [precepts] that your Lord has revealed to you of wisdom. (17:39)
These are the signs of the wise Book (31:2)

What is wisdom in the eyes of Allah?

The original meaning of the word “Hikmah” is wisdom, knowledge and tolerance and the ability to use your knowledge in the best way; but Allah The Almighty prefers some special kinds of wisdom. The verses of the Quran and the hadiths, try to clarify the true meaning of wisdom from Islamic sight.

Obedience towards Allah 

•    Abu-Basir, one of the brilliant pupils of Imam Sadiq (AS) once asked him about the verse; “He grants wisdom to whomever He wishes (2:269)”. Imam Sadiq (AS) replied, “That (Wisdom) is obeying Allah and knowledge about Islam” (4)
•    Imam Baqir (AS) also says that “Hikmah” means: “not to commit the sins that Allah has ordained for it the Hell as a punishment” (5)
•    Once Prophet Muhammad (PBUH & HP) asked a group of people who they are.
They said that they are some faithful people.
The Prophet (PBUH & HP) asked: “What are the signs of your faith?”
They said: “We are content about what Allah has planned for us and we are submissive to the order of our God and we trust in him for everything.”
The Prophet said: “You are so knowledgeable and wise the way that your wisdom can almost make you like prophets.” (6)

Knowing our Imams

Imam Sadiq (AS) about the verse “…and he, who is given wisdom, is certainly given an abundant good (2:269)” said ,“The abundant good is knowing Imam Ali (AS) and the other Imams (AS)” (7) 
He also said: “(The “Hikmah” mentioned in the verse is) obeying Allah and knowing the Imam (of your time)”
In Arabic, the word “جهل” (Jahl) means “Ignorance”, which can be considered the opposite of “Hikmah”. So anyone who is not “Hakim” (wise) is “Ignorant” in Islamic culture. There is a hadith narrated from the Prophet (PBUH & HP) in which he said:

Anyone who dies while they don’t have an Imam will have died like a person in the ages of ignorance (8)

This hadith has been narrated by all Muslims’ Sunnis and Shiites and the authenticity of this record is undeniable. 
About knowing the Imam, Imam Sadiq (AS) also said:
Anyone from among the followers of Prophet Muhammad (PBUH & HP) who understands the status and the rights of their Imam, will find how delightful  having faith is.(9)

Understanding Religion

The last meaning of “Hikmah” mentioned in the Hadiths is “Fiqh” (jurisprudence) which means “Understanding”. In Islamic culture, this word is  employed  to define a deep understanding of religion and profound knowledge about  it . (10)
Imam Sadiq (AS) said: 

“Hikmah is the knowledge about religion and understanding it (Fiqh). Therefore, anyone who understands the teachings of the religion is a “Hakim” (a wise person). Indeed above all, Satan wishes the ones who deeply understand religion, to be dead.” (11)
The Holy Prophet (PBUH & HP) said: 
Allah has given me the Quran and he also gave me Hikmah just like the Quran and every house which therein is no Hikmah is nothing but a ruined place. So learn Fiqh and get to know the religion so that you don’t die like ignorant people. (12)

To wrap up, in the Islamic view, “wisdom” means knowing how to live as a good servant of Allah and living the same way. As you see, all the meanings mentioned in the Quran and the Hadiths are about knowledge of religion and living the way religion indicates. Knowing your Imam (who is the leader Allah has chosen for you) is the best way to understand what you should do and how you should obey the orders of Allah.  It is then obvious that all these different meanings and teachings employ a common concept which is obeying the order of Allah after having enough knowledge about it.  
It is then obvious that all these different meanings and teachings employ a common concept; obeying the orders of Allah after gaining and enjoying competent knowledge about them.

Resources

1.  https://dictionary.cambridge.org/dictionary/english/wisdom 
2. Al-Ain, Khalil ibn Ahmad al-Farahidi, vol.3, pg.66
3. Al-Kafi, Sheikh Koleini, vol.1, pg.13
4. Tafsir noor ath-Thiqhlain, al-Huvaizi, vol.1, pg.287
5. Tafsir, Al-Ayyashi, vol.1, pg.151
6. At-Tohid, Sheikh Saduq, pg.371
7. Tafsir noor ath-Thiqhlain, al-Huvaizi, vol.1, pg.287
8.  Musnad Ahmad ibn Hanbal, vol.28, pg.88
9.  Basa’ir ad-Darajat, Muhammad ibn Hassan as-Saffar, pg.412
10.  Sihah, al-Johari, vol.6, pg.2243
11.  Tafsir, al-Ayyashi, vol.1, pg.151
12.  Majma al-Bayan, Sheikh at-Tabarsi, vol.2, pg.194
     

Every year on the 20th of Safar, the second month in Hijri Calendar, a huge number of people from all over the world, Muslim or even non-Muslim, gather in Iraq to take part in a symbolic walk. People of Iraq for months before this day, eagerly prepare themselves to welcome the visitor of Imam Hussain’s (AS) shrine. They find it a great honor to serve those who are participating in this event and are paying a visit to Imam Hussain’s (AS) shrine. Iraq on this period becomes the site of the purest and most humane manifestations. 

But, one might wonder what is the reason behind all these efforts? Why would someone walk a long distance, bearing all the difficulties on his/her way, to reach a shrine? What is it that drives this huge number of people here? 

In what follows, you will find out about Arbaeen and the ceremonial walk on this day.

1. When is Arbaeen?

Arbaeen is the Arabic word for forty, and it marks the 20th of Safar, the fortieth day after Imam Hussain’s (AS) martyrdom on the day of Ashura, who was martyred in the event of Karbala along with his companions in the cruelest and most inhumane way possible. 

2. What Happened on Arbaeen at 61th of Hijri year? 

After the event of Karbala, Imam Hussain’s (AS) family including his sister Lady Zainab (AS) and his son Imam Sajjad (AS), were taken as prisoners to Sham (Damascus) to Yazid’s court. Imam Hussain’s (AS) head was also sent to Yazid’s court along with his family [1].

According to some historical accounts [2], some of the members of Imam Hussain’s (AS) family after being released from the bondage of Yazid forces, returned to Karbala from Sham (Today’s Damascus) to visit Imam Hussain’s (AS) grave. Also, some believe that Imam Hussain’s (AS) head which was taken to Sham by Yazid’s army was brought back to Karbala on this day and buried with his body [3] & [4]. 

3. What is the philosophy behind visiting Imam Hussain’s (AS) shrine?

But these are not the only reasons behind the commemoration of Arbaeen every year. Visiting Imam Hussain’s (AS) shrine is one of the recommended deeds at any time of the year, especially in Arbaeen [i]. Also, Imam Baqer (AS) enumerates the several benefits of this action. These include the increase in wealth, acceptance of prayers by Allah, longer life, and pardoning of the sins [5].  

But, why would visiting Imam Hussain’s (AS) shrine be of such importance? It is not where we are visiting, but who we are visiting and what he taught us that makes this action so worthy of attention. In fact, in paying a visit to Imam Hussain’s (AS) shrine, we try to remind ourselves of these two messages:

     1. To never surrender to injustice and oppression, as Imam Hussain (AS) did not yield to the tyrant of his time.

    2. To always be eager in improving and reforming ourselves and our society, as Imam Hussain (AS) answered people’s call for improvement and did his best to help them, despite the fact that his will remained unfulfilled due to his enemies’ deception.  

Now, we can better understand the Prophet’s (AS) conviction that Imam Hussain’s (AS) personality would forever guide the humanity toward everlasting peace and success. And ignoring the values he emphasized would cause eternal distress and calamity [6].  

4. Why visiting Imam Hussain’s (AS) shrine is recommended on special occasions (e.g., Arbaeen)?

Visiting Imam Hussain’s (AS) shrine is more recommended on some occasions, especially Arbaeen which could be because of the history of this day. Yet, this does not mean that this action cannot be done on any other days of the year.    

But, this is not the only reason for this huge number of people to gather together on this day. In fact, they are all driven by the lasting message that Imam Hussain (AS) left for us through his courageous and rightful movement. That is the urge to stand against injustice, oppression and to strive in the way of improving their situation socially or individually. Arbaeen walk is where people reunite to commemorate these lessons of Imam Hussain’s (AS) revolution together. 

5. How long does it take to walk from Najaf to Karbala?

The journey on foot from Najaf to Karbala which is called Arbaeen walk takes almost three days. But, everything is ready for those who want to take part in this life-changing walk. Many camps (Mawkib) are prepared on this way by people voluntarily which provide free food and accommodations for the respected pilgrims of Imam Hussain’s (AS) shrine. 

6. How many people gather on this walk annually?

Muslim or non-Muslim, a large number of people take part on this journey.  According to the Independent: “Nusayyef al-Khattabi, who heads the Karbala provincial council, said he expected the total number of visitors over several days to range ‘between 17 million and 20 million’” [8].

7. Is  Arbaeen’s Walk an obligatory ritual? 

While Arbaeen Walk is one of the greatest Muslim gatherings, it is not an obligatory ritual. In other words, it cannot be considered as one of the practical principles of Islam (e.g., prayer (Salat), fasting (Sawm), Khums, Hajj, etc.) which a Muslim is required to perform. Participating in this journey is totally up to your choice, decision, and interest. Yet, Arba’een walk is a recommended ritual which carries many spiritual benefits for the one who takes part in it. 

8. Who can participate in Arbaeen’s walk?

Anyone, from any nationality, religion or any age, can join this walk. This is a gathering of those who respect humanity and peace, are after making changes for the better and do not surrender to injustice. As Imam Hussain (AS) believed being free-spirited and honest is what guarantees human dignity [9]. So, as long as you believe in these values, you are most welcomed on this journey. 

9. How can you join Arbaeen’s walk?

It only takes your decision. And you might need to prepare some necessary things to carry with you in this walk. Also, it is better to be both physically and spiritually ready for this experience. Since, like many other life-changing experiences, it has its own hardships and challenges.

Note that the walk starts three days before Arba’een so that you will reach Imam Hussain’s (AS) shrine on Karbala on this day. So, you should start your journey from the 17th of Safar and finish it on 20th.  

10. What if we couldn’t travel to Karbala? What can we do instead?

While visiting Imam Hussain’s (AS) shrine on Arba’een is a recommended deed, what matters most is to be aware of the philosophy behind this action. Imam Hussain’s (AS) universal and all-encompassing message, is not limited to an especial location or a specific time [10].

We can declare our commitment to Imam Hussain’s (AS) cause anywhere and at any time. So, if you couldn't manage to take part in Arba’een’s ceremony, there are some actions that would help you benefit from this occasion spiritually, such as reciting the Ziarat al-Arba’en or Ziarat al-Ashura. The least you can do is to send your peace and salutations to Imam Hussain (AS) wherever you may be:

Peace be upon Hussain (AS) and Ali ib al-Hussain and Hussain’s children and Hussain’s companions [11] 

Notes:
[i] Imam Hassan al-Askari (AS) told in a hadith that, among the signs of a faithful person, is visiting Imam Hussain’s (AS) shrine [7].

References:

1. for more information see Salam Islam’s ebook: 40 Points about Imam Hussain (AS) and the Event of Karbala
2. Ibn Tawus, 'Ali b. Musa, Al-Luhuf 'ala qatla l-tufuf, Uswi, Qom, 1414 AH.
3. Al-Biruni, Abu Rayhan, The Remaining Signs of Past Centuries, p.331.
4. Qazi al-Tabataii, Muhammad Ali, A Research on the first Arba’een of the Leader of Martyrs (Imam Hussain (AS)), vol.3, p.304. 
5. Mustadrak al-Wasail, vol.10, p.239. 
6. Hashim al Bahrani, Al-Burhan Fi Tafsir al-Quran, vol.3, p.232. 
7. Shaykh Tusi, Tahdhib al-Ahkam , vol.6, p.52.  
8. Bihar al-Anwar, vol. 45, p.49.
9. Mustadrak al-Wasail, vol.10, p.309.
10. Ziarat al-Ashura