During the period of the holy prophet’s (s.a.w.a.) appointment and proclamation, he entrusted the people with two precious souvenirs out of divine inspiration.
“I leave with you two weighty things: the Book of Allah and my offspring.” 
This he said at the time when he himself bore the responsibility of explaining and interpreting the commandments and doctrines and he acquainted the Muslims with different levels from various angles of religion. However, he entrusted the task of interpretation and explanation of diverse religious matters to his successors after him and named them the other weighty thing (ثقل) on par with the Qur’an.
The pure and honourable Imams (a.s.) too took charge of this divine mission in line with the holy Qur’an and the prophet’s (s.a.w.a.) Sunnah and prevented distortions in belief, wrong interpretations of holy Qur’an and Islamic doctrines. For this reason, along side the holy Qur’an, we must search the Islamic matters and the prophet’s (s.a.w.a.) Sunnah in the sayings of the holy Imams (a.s.). These sayings are commonly known as“Hadith or traditions” .
At a short glance, we can classify the sayings of the holy prophet (s.a.w.a.) and Imams as follows:
1- In the form of preliminary Hadith and sayings: They (p.b.u.t.) would explain to one or more people matters concerned with belief or ethics or Tafsir (interpretation) or Fiqh (jurisprudence) or history etc. These traditions was at times in the form of Hadith-e-Qodsi that was narrated from the Almighty Allah (except Qur’an) or in the form of simple Hadith.
Example for the first category: Hazrat Reza (a.s.) said: Musa-ibn-Jafar narrates from Jafar-ibn-Muhammad from Muhammad-ibn-Ali from Ali-ibn-Husain from Husain-ibn-Ali from Ali-ibn-Abi Talib from the holy prophet (s.a.w.a.) from Gabriel from Meka’eel from Israfeil from Luh from Qalam that Allah says:
“The Vilayat (authority) of Ali-ibn-Abi Talib (a.s.) is My castle. Anyone who enters My castle is safe from My chastisement.” 
As an example for the second category, the holy prophet (s.a.w.a.) said:
“O Ali you are the best of all men; anyone who doubts about you is an unbeliever.” 
2- In the form of speeches and sermons: Amongst the numerous specimens are the invaluable sermons of Amir-ul-Mu’minin (a.s.) just as he says in one sermon :
“The Imams are from Quraish; from sub-tribe of Hashim; and except for them nobody is qualified for the post of Imamate.”
Other Imams too have presented their sermons on various topics where some of them can be seen in the form of collective traditions.
3- In the form of debates and discussions with one or more people (in matters of belief, Tafsir etc)
An example of such debates is the case of Imam Sadiq’s (a.s.) debate with the atheists. One example: The opponents said: How does Allah become pleased and angry for the happiness and anger of Fatemah (a.s.)? Imam (a.s.) replied: You narrate tradition that says Allah becomes pleased because of His faithful slave’s happiness and turns angry because of his anger. Isn’t the holy prophet’s (s.a.w.a.) daughter a woman of faith? They replied: ‘You have spoken the truth!
4- In the form of invocation: Its worthy to mention that most of the lofty and sublime sayings of the noble Imams have been presented in the form of invocation and supplication.
Imam Sajjad (a.s.) would place his face on the earth at mid-night and would say:
“O Allah! Thou are Magnificent who does not turn back hopeless the one who calls Thee and Thou are aware of the one who seeks proximity towards Thee and only Thou fulfill their needs.” 
Also, he (a.s.) says:
أسألك الروح و الراحة عند الموت والعفو عني حين ألقاك
5- In the form of Ziarat: Our divine leaders have described numerous matters pertaining to belief like monotheism, recognition of Imam etc in the form of Ziarat:
In Ziarate-Amin’allah which has come down about Amir-ul-Mu’minin (a.s.) and is recited for all the Imams, it begins as such:
السلام عليك يا أمين الله في أرضه و حجته علي عباده. السلام عليك يا أمير المومنين
“O Allah make my soul firm with respect to Your decree and make me pleased with Your decision and judgement.”
6- In the form of inscription, letters and treatise: Many a times, the holy prophet (s.a.w.a.) and the noble Imams (a.s.) would note down points on belief, ethics, jurisprudence etc in the form of letters and dispatch them to near and far places. For instance, Imam Amir-ul-Mu’minin (a.s.) wrote for his representative about charity:
“Set out on the path of piety of the Unique Allah (Who has no partner). Do not create fear in any Muslim and do not collect charity from him by force and do not ask more than the required right of Allah in wealth….” 
7- In the form of question and answers: Question and answers is one of the best and most natural way for understanding and explanation and the holy Qur’an gives prime importance to this matter. On the one hand, Allah addresses the people and says:
“So ask the followers of the Reminder if you do not know” . (Qur’an, 16:43)
On the other hand, in fifteen instances, He reminds the holy prophet (s.a.w.a.) that: “يسألونك ” They ask you and you reply them in such and such manner.
In the noble traditions too, on numerous occasions, the Imams (a.s.) were questioned on matters like belief, ethics and jurisprudence and they replied the people accordingly.
Now, we shall set forth as a good luck, two such specimens of question and answers by Imams (a.s.):
a) Ma’mun asked Imam Reza (a.s.): O Abul-Hasan explain to me how your great grandfather Ali-ibn-Abi Talib is the distributor of paradise and hell? Imam (a.s.) replied: ‘O leader of believers. Didn’t your father narrate from his fathers from Abdullah-ibn-Abbas who said: I heard the prophet (s.a.w.a.) saying: Love of Ali (a.s.) is belief (faith) and enmity to him is infidelity?”
Ma’mun said: Yes.
Imam (a.s.) said: So he is the distributor of paradise and hell.”
Ma’mun said: O Abul-Hasan, may Allah not make me live after you. I bear witness that you are the heir to the prophet’s knowledge.
Aba Sult Herawi says: When Imam Reza (a.s.) returned to his residence I said: O the son of Allah’s messenger, how nicely you replied the caliph (Ma’mun)! He said: ‘O Ab Sult, I replied him from the same angle and motive he set forth his query. Certainly, I heard my father narrate from his fathers that Amir-ul-Mu’minin (a.s.) said: ‘The prophet (s.a.w.a.) informed me: ‘O Ali, you are the one distributing heaven and hell on the day of resurrection. You would say to the Fire: He is from me and that one for you.”
b) Abdul-Azeem Hasani said: I asked Hazrat Javad (a.s.): My master, I hope you are that Qaem from the prophet’s Ahl’ul-bayt who would fill the earth with equity and justice just as it would be filled with injustice and tyranny. Hazrat (a.s.) replied:“All of us rise (are Qaem) to Allah’s commands and guide (the people) towards His religion. But the Qaem through whom Allah will cleanse the earth off infidelity and disbelief and fill it with equity and justice is someone whose birth is hidden and he is concealed from the people and they are forbidden from uttering his name. His name and agnomen is the same as the prophet’s (s.a.w.a.) name and agnomen. He is someone for whom the earth will unfold its treasures and every hardship would be managed by him and his companions numbering 313 men equal to the number of people of Badr would gather around him from near and far and these are Allah’s words Who says: “And wherever you are, Allah will gather you; verily Allah is Powerful over all things.”
When this number of people would collect with utmost sincerity, Allah will manifest the Qaem’s affair. At that moment, his soldiers would number ten thousand and he will rise by Allah’s command. He will fight Allah’s enemies until the Almighty Allah becomes pleased.”
It’s worthy to mention that imparting and explaining matters in the form of question and answer has the following advantages:
It’s beneficial to the questioner because the reply is mooted at his level of knowledge and understanding.
Due to face-to-face discussion between addresser and addressee and brief reply, the matter remains in the mind of questioner.
Any extra saying that is not concerned with the questioner is avoided unless he personally requests for such additional information.
This manner enables the seeker of knowledge to learn better the style of questioning and he acquires his reply much quicker.
Usually, in question and answer form, the“matter under consideration is mooted as per time or era” . In some scholarly matters, its roots and contents may be old but the style and form of question varies from time to time. For instance, question and answer acquaints a student about a matter that is appropriate of that time.
Very often, tens of questions of one questioner is solved and replied from various angles in one sitting.
In session of questions and answers, the questioner finds courage of setting forth his question and problem and take steps for finding their solution.
By question and answer, an affectionate relationship is established, particularly if conducted in oral and face-to-face manner. By friendly relation between the teacher and student, both can come to an intellectual agreement in a much better manner. The learner pursues the teacher and reaches perfection.
Respected readers, these and other unrevealed points have forced scholars throughout history to possess detailed writings in reply to questions of the people of their respective time. For instance, the late Shaikh Agha Bozorg Tehrani in Vol 5 of his book“Az-Zariah” has recorded 424 books under the title ‘Reply’ and 250 books named as“Replies” .
One specimen of such book of the past is the writing of Shaikh Mufid named“Al-Masael al-Okbariyah” which in Vol 6 of his collection of literary works, on page 25 till 135, he has arranged 51 questions and answers on various topics like belief, tafsir, hadith and fiqh. Amongst the recent works, we can name the book“Al-Muraje’at” written by Sayyed Abdul-Husain Sharafuddin Musavi wherein is found questions and answers, discussions and debates in the form of 112 letters on Shia and Sunni sect, Imamate and caliphate exchanged between him and Shaikh Sulaim Bushri, the head of Al-Azhar university of Egypt of that time.
By following the path of Qur’an and Imams as well as past scholars, this writer was instigated to set forth matters in the form of question and answers for the addressees. Thus, I hope the scholars give their guidelines and I hope Imam-e-Zaman (a.t.f.s.) assists me and even though I don’t find myself worthy of such work, nevertheless, I only intend to serve and express my gratitude towards my holy master and I hope for forgiveness and generosity.
Sayyed Husain Husaini