Hazrat Imam al-Mahdi (A.S.) is the twelfth and last of the chain of the Purified Imams and the divine successors (A.S.)he was born at the time of dawn on Friday the 15th of Shaban 255 A.H. in the city of Samarrah. (Kamaaluddin vol. 2, Pg. 428, 433 424, 430)
His respected father is Imam Hasan al-Askari (A.S.), his beloved mother is Janab-e-Nargis Khatoon (r.a), she was in the side of her father from the descendant of Caesar of Rome and descendant of Shamoon the vicegerent of Hazrat Isah (a.s) in the side of her mother. "Kamaaluddin vol.2 Pg. 420, 424,"
This exalted personality has the same name as the holy prophet (S.A.W.).His titles are Mahdi, Hujjat, Qaem, Montazer, Sahibuzzamaan and Khalaf-e-Saleh his most famous honorific however is al-Mahdi (A.S.). "Al Fusoolul Muhimma Pg.292, Nurul Absaar Pg. 168"
Ibn Khallikaan writes; "His well-known title is Hujjah, the Shiites know him by the titles Montazar, Qaem and Mahdi" (Wafayatul Ayaan vol.4 Pg 176).
Mohaddith an-Noori a great scholar has collected 182 titles of Imam al- Mahdi (A.S.) from the Islamic texts, each of these titles signify each of his virtuous qualities (Najm-us-saaqib Pg. 41-98).
The tyrant Abbasid rulers were aware of the prophecies of the holy Prophet (s.a.w.w.) that the son of Imam Hasan al-Askari (A.S.) that is going to be named al-Mahdi (A.S.) will appear to remove all kinds of corruption and tyrannies, hence they planned eliminating the child when he is born, So for the above reason the birth of Imam al-Mahdi (A.S.) was kept a secret like that of Hazrat Ibrahim (A.S.) to the extent that no one knew about the existence of Hazrat (A.S.) except his family and the most faithful ones among his Shiites.
In spite of this whenever there was an opportunity Imam Hasan al-Askari (A.S.) showed his son to his faithful followers so that in future they may follow him, this was in order so that the Shiites may remain firm upon the righteous path and not to be led astray.A servant Abu Ghanim says: "Abu Mohammed (a.s) has a son whose name is Muhammad" on the third day of his birth he brought him before his companions and said: "After me he is the master of all your affairs, he is my successor, he is the same 'Qaem' that all are in anticipation for his appearance when the earth will be fraught with injustice and oppression, then he will reappear and fill the earth with justice and righteousness."(Kamaaluddin Vol. 2 Pg. 431)
The early years of his life were spent in the usual way but lost his respected father when he was in his fifth year. (Al Kaft Vol. 1 pg. 503)
After this tragic event the responsibility of guiding the Shiites was transferred to him, by this time he has already possessed all the qualities and divine knowledge that God gave to the previous Imams before him in the same way prophet Yahya (A.S.) was given in his childhood and prophet Isah (a.s) was honored with prophet hood during his infancy. (Quran: sura Maryam, Ayat 12 and 30)
Despite the fact that holding the divine office of authority (al-Wilayah) is a responsibility on all the Imams (s.a.) but the efforts made by the enemies to eliminate the twelfth Imam (a.s) reached the highest peak, due to this reason he was given a divine command to go on occultation, he has being away from the sight of people and he had to fulfill all the duties of an Imam (a.s).
It is said that the hidden life of Imam al-Mahdi (A.S.) is not something extraordinary rather it has been confirmed in the life of many Prophets and Imams (s) it has been observed that they were in concealment from the people sometimes, the holy Quran records the concealment of some prophets (s) like prophet Ibrahim (Sura Maryam: 48-49), prophet Musa (Sura Qasas:21-22) and prophet Isah (Sura Nisa: 157).
The holy Prophet and the Imams (s) had pointed out to the people the impending occultation of their last proof (Imam al-Mahdi a.s.) in order to avoid any doubt and misunderstanding in regard to this issue.The occultation (Ghaibat) of the twelfth Imam is of two stages. One is the lesser occultation and the second is the greater occultation.
Imam Jaffar as-Sadiq (A.S.) said: 'There are two occultation for the Qaem i.e. Imam al-Mahdi (A.S.)one is short and the other one is long, the special Shiites are the only ones to know where about of Imam during the lesser occultation but only his faithful servants know where about of him during the long occultation." (Al Kafi Vol. 1 Pg. 340. Ghaibat Nomani Pg. 180)
The commencement of the lesser occultation was on 260 A.H. and lasted for 69 years in accordance to the famous report in circle but some eminent scholars like sheikh Mufeed and Sayid Muhsin Amin Ameli were of the belief that the commencement of the lesser occultation was from the time of his birth. (Al Kafi Vol. 1 Pg. 340. Ayan ush shia Vol. 2 Pg. 46) they had this belief because from the advent of Imam al-Mahdi he was concealed from the common people, therefore in accordance to their belief the period of the lesser occultation was seventy-four years.
During the period of the lesser occultation Imam al-Mahdi (A.S.) appointed his deputies from his faithful Shiites by himself, all of them that were four in number succeeded each one another and continued fulfilling the duty of intermediaries, they do take problems and questions to Imam (a.s) and conveyed the solutions and answers from the Imam (a.s) to the people.The first deputy was Janab Abu Amroo Usman bin Saeed Amri, he was previously a representative of Imam Hasan al-Askari (a.s) (Ghaibat-e-Tusi Pg. 353)
Shaykh Tusi writes: On the fortieth day of Imam's birth the Shiites were sitting in the company of Imam Hasan al-Askari (a.s) when Imam Askari (a.s) wished that they should recognize the proof of God after him.....Suddenly a handsome child was brought before them that resembles Abu Mohammed (a.s) then Imam al-Askari (a.s) said: "He is your Imam and successor after me, obey him and don't go astray after me (after my death) otherwise your religion shall be destroyed and you will be annihilated know that after today you shall not see him even if you spend your whole life looking for him, therefore accept what Usman tells you, obey his commands and listen to what he says because he is the one taking the responsibility as a representative of your Imam (A.S.). (Ghaibat-e-Tusi Pg. 357)
Muhammad bin Usman the pious son of the first deputy succeeded his father as the second deputy to Imam (a.s) after his demise. (Ghaibat-e-Tusi Pg. 362). Shaikh Tusi has recorded the letters sent by Imam Hasan al Askari and Imam al-Mahdi (a.s) through Usman bin Saeed and his son Abu Jafar Mohammed ibne Usman to the Shiites, these letters contain commands, prohibitions and replies to the questions of the Shiites. (Ghaibat-e-Tusi Pg, 356).
Mohammed ibne Usman passed away from this world at the end of Jamadi-ul-Awwal in the year 304 or 305 A.H. (Ghaibat-e-Tusi Pg.366)
During the time of his illness while lying on his sickbed, the Shiites and their children came and surrounded him, they asked him that who should be consulted in regard to the new incidences on your behalf? He answered, " This Abul Qasim Husayn ibn Ruh ibne Bahr Nawbakhti is the successor, the intermediary between you and the master of all affairs (Imamul-Mahdi) and his agent, he is trustworthy and reliable Consult him and rely on him on the issues that are of great importance, I have been ordered to make this announcement and I have made it. "(Ghaibat-e-Tusi Pg. 371-372)
Husain ibn Ruh Nawbakhti was one of the agents of Muhammad ibn Usman in Baghdad, he had been working closely with him for a long time, these agents used to be in contact with the people and when ordered they handed over the goods to them (Gaibat-e-Tusi Pg. 369/372), Husain ibn Ruh died in Shaban 326 A.H (Ghaibat-e-Tusi Pg. 387).
The last ambassador was Abul-Hasan Ali ibn Mohammed Seymoori, he became the fourth deputy of Imam al-Mahdi (a.s) in accordance to the will made by Husain ibn Ruh, he died after three years on the 15th of Sha'ban 329 A.H,. (Ghaibat -e- Tusi Pg. 394)
The graves (tombs) of these four respected deputies (Nawwab al -Arba as they are commonly known) are there in Baghdad. (Ghaibat -e- Tusi Pgs. 358, 366. 376, 396).
The most sensitive and crucial period of lesser occultation was when Ali ibn Mohammad the fourth deputy passed away, since his death was the advent of the major occultation and people have been in contact with their Imam through him before his demise.Ali ibn Mohammed Seymoori received the following communication from Imam al-Mahdi (A.S.) six days before his death: "..so be prepared but don't appoint any one to replace you, since the period of my major occultation begins from the day of your death. Henceforth no one shall see me unless and until Allah makes me appear, my reappearance will take place after a very long time when the world will be fraught of injustice and violence". (Kamaaluddin Vol.2 Pg.516 Ghaibate Tusi Pg.395)
Eventually the shining sun of the divine proof went behind the curtain of occultation completely while the period of communication with Imam (through four deputies) has came to an end, despite the fact that he is in occultation but he still remain the Imam of this time and the universe and also the divine proof, in spite of his hidden body from us but his commands are clear and comprehensible.
The leader of the faithful ones Ali (A.S.) announced from his pulpit at Kufa: "Even if the human body of the divine proof is hidden while guiding people but his knowledge and manners will be clear for them to follow" (Kamaaluddin vol. I Pg.302).
It is obvious that the knowledge and practice of the Imam of age (a.s) is perfect like holy Quran exactly as how was the practice, saying and… of the Holy Prophet (S.A.W.), it is incumbent on the people of faith i.e. the believers to act in accordance to the commandments of Quran and Sunnah i.e. saying and practice of the infallibles, and refrain from what have been forbidden on them, the Holy Prophet (S.A.W.) said: "I leave behind two weighty things among you, the book of Allah and my progeny, my Ahlul-Bait (a.s) If you adhere to those two you shall not go astray and know that these two shall not separate till they meet me at Hauz (Kauthar)" (Yanabiul Mawaddah Pg. 35)
During the period of the greater occultation when there is the impossibility of communication with Imam (A.S.) at the time of desire, the people have been commanded to follow the true teachings of the Quran and the infallible ones among the progeny of the Holy Prophet (S.A.W.) i.e. the Ahlul- Bait (A.S.) through the pious, religious scholars and the just ones among the jurists, people must follow them in order to know those things that are incumbent on them.
Imam as-Saadiq (A.S.) says: "And among the jurists (Fuqaha) are those who protect themselves (from sins), guard their religion, defy their carnal desires and are obedient to their master, it is incumbent upon the people to follow them, such characteristics are found only with few of the followers of the infallible progeny of the prophet i.e. followers of Ahlul-bait (a.s)) and not all". (Tafsir al-Imam Pg. 300)
The jurists issue decrees for the people and explain to them truth about faith, they endeavor to fulfill the exalted duty of preparing the grounds for the reappearance of their master, Hazrat al-Mahdi (a.s) So that by the coming of Hazrat (A.S.) the Islamic faith might have become strong and that he shall then fill the earth with justice and equity.