The occultation (Ghaybah) of the twelfth Imam consists of two phases: one is Ghaybah al-Sughra (The lesser occultation) and the second is Ghaybah al-Kubra (The greater occultation).
Hazrat Imam Al-Mahdi (‘a) is the twelfth and last of the chain of the Purified Imams (‘a) and the divine successors. He was born at the time of dawn, on Friday the 15th of Shaban 255 A.H. in the city of Samarrah.
His respected father is Imam Hasan al-Askari (‘a). His beloved mother is Janab al-Nargis Khatoon (ra). She was the descendant of the Caesar of Rome from her father’s side and from her mother’s side she had descended from shamoon the vicegerant of Hazrat Isa (‘a).
This exalted personality has the same name and kuniyah (agnomen) as the Holy Prophet (S). His titles are Al-Mahdi, Hujjat, Qa’im, Muntadhar, Sahibuzzaman and Khalaf al-Saleh. His most famous honourific however is Al-Al-Mahdi (‘a).
Ibn Khallikaan writes; “His well-known title is Hujjat. The Shi’as know him by the titles, Muntadhar, Qa’im and Al-Mahdi”
The great scholar Mohaddith al-Noori has collected 182 titles of Imam Al-Mahdi (‘a) from the Islamic texts. Each of these titles signify each of his virtuous qualities.
The tyrant Abbasid rulers were aware of the prophecies of the Holy Prophet (S). That the son of Imam Hasan al-Askari (‘a) by the name of Al-Mahdi will appear to remove all kinds of corruption and tyranny; hence they planned to eliminate the child when he is born. Due to this the birth of Imam Al-Mahdi (‘a) was kept a secret like that of Hazrat Ibrahim (‘a). So much so that except for the most trusted of the Shi’as and his own family, no one knew of the existence of Hazrat (‘a). In spite of this whenever there was an opportunity, Imam Hasan al-Askari (‘a) showed his son to his trustworthy followers; that in future they may follow him. This was in order that the Shi’as may remain firm upon the right path, and not be led astray. A servant Abu Ghanim says:
“Abu Muhammad (‘a) 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 your Master of the affair, he is my successor, he is the same ‘Qa’im’, who is awaited by alt When the earth will be fraught with injustice and oppression then he will reappear and fill the earth with justice and righteousness.”
The early years of his life were spent in the usual way. When he was in his fifth year, he lost his respected father.
After this tragic event the responsibility of guiding the Shi’as was transferred upon him. At this time, Hazrat (‘a) possessed all the qualities and the divine knowledge that was bestowed upon the previous Imams (‘a), by the Almighty. In the same way as Hazrat Yahya (‘a) in his childhood and Hazrat Isa (‘a) in his infancy was favoured with the divine office of Prophethood by Allah.
Although all the Imams (‘a) were holding the divine office of wilayat, the efforts of the enemies to eliminate the twelfth Imam (‘a) were maximum. Hence Imam az-Zaman (‘a) was entrusted to Ghaybah and being away from the sight of people, he had to fulfill all the duties of an Imam.
It is said that the concealed life of Hazrat Al-Mahdi (‘a) is not something extraordinary. Rather, in the life of so many Prophets (‘a) and even Imams (‘a) it is seen, that they were at some time, in concealment from the people. The Holy Qur’an records the concealment of various prophets (‘a) like Hazrat Ibrahim (‘a), Hazrat Musa (‘a) and Hazrat Isa (‘a).
The Holy Prophet (S) and the Imams (‘a) had pointed out to the people the imminent occultation of their last proof (Imam Al-Mahdi-aj), so that no doubt or misunderstanding should remain, regarding this problem.
The occultation (Ghaybah) of the twelfth Imam consists of two phases: one is Ghaybah al-Sughra (The lesser occultation) and the second is Ghaybah al-Kubra (The greater occultation). Imam Ja’far Al-Sadiq (‘a) said:
‘There are two occultations for Qa’im. One is short and the other prolonged. In the short occultation only the special Shi’as will know of his whereabouts. And in the longer occultation only his trustworthy servants will know where he is”.
Reasons for the Occultation of Imam Al-Mahdi (‘A)
Free From Allegiance of Every Tyrant
Amir Al-Mu’minin Ali (‘a) said,
“Certainly’, when the Qa’im from among us shall arise, he will not have the allegiance of any one upon his neck. It is for this reason that his birth is secret and his person is in Ghaybah.”
It must be mentioned that all of our Imams had to pledge allegiance to every tyrant ruler except for a short period during the rule of Umar Ibn Abdul Aziz. This was because, on the face of it, it would seem that they are not against the ruler, In this way they could protect Islam. In the absence of popular support, the Imams were left alone and thus they entered into an understanding with the rulers. Thus even Imam Husain (‘a) for a particular period did not find it necessary to revolt against the regime of Muawiya.
In this regard Hazrat Al-Mahdi (‘a) says:
“Verily each of my ancestors had the oath of allegiance, upon their necks, of their contemporary tyrant rulers. But I will reappear at such a time that I will not have any tyrant’s allegiance upon my neck.”
- Test of the People
Imam al-Kazim (‘a) said,
“My son! When the fifth descendant of the seventh of the Imams is not visible to you! It is when Allah will test your belief. Ghaybah is inevitable for the Master of this affair.
Till the time when the religion is completely transformed, and only a few people will have belief in him. My son! That Ghaybah, It is a trial through which Allah, the Almighty tests His servants.”
- Fear of the Enemy
Imam Musa al-Kazim (‘a) said,
“The Qa’im is the one who will purify the earth from the enemies of Allah, the High and the Mighty. And he will fill the earth will justice and equity just as it is filled with injustice and tyranny. He is the fifth of my descendants. He will go into occultation due to the fear of his own (life).”
According to common sense it is necessary for man not to throw away his precious life without a legitimate aim. Thus, the prophets (‘a) and the Imams (‘a) have taught the people that it is their duty to protect their life under every circumstance and should never put their life in danger. Therefore it is the duty of the last of these exalted personalities to protect himself till the time of his reappearance when he will establish the new world order.
- Weakness and Lack of Co-Operation of the People
Imam Al-Mahdi (‘a) said.
“If our Shi’as; may Allah help them in His obedience; would have fulfilled their covenant with united hearts then there would have. been no delay in our meeting, and they would have been blessed with our visitation at the earliest, along with the recognition of truth and confirmation of our rights.”
 Kamaaluddin vol. 2, Pg. 428, 433 424,430.
 Kamaaluddin vol.2 Pg. 420,424.
 Al Fusoolul Muhimma Pg.292, Nurul Absaar Pg. 168.
 Wafayatui Ayaan vol.4 Pg 176.
 Najm-us-saaqib Pg. 41-98.
 Kamaaluddin Vol. 2 Pg. 431.
 Al Kafi, Vol. 1 pg. 503.
 See Qur’an, Sura Maryam, Ayat 12 and 30:
يَا يَحْيَىٰ خُذِ الْكِتَابَ بِقُوَّةٍ ۖ وَآتَيْنَاهُ الْحُكْمَ صَبِيًّا
“O Yahya! Take hold of the Book with strength, and We granted him wisdom while yet a child” (19:12).
قَالَ إِنِّي عَبْدُ اللَّهِ آتَانِيَ الْكِتَابَ وَجَعَلَنِي نَبِيًّا
“He [Isa – Jesus] said: Surely I am a servant of Allah; He has given me the Book and made me a prophet” (19:30).
 See Qur’an, Sura Maryam, Ayat 48-49:
وَأَعْتَزِلُكُمْ وَمَا تَدْعُونَ مِنْ دُونِ اللَّهِ وَأَدْعُو رَبِّي عَسَىٰ أَلَّا أَكُونَ بِدُعَاءِ رَبِّي شَقِيًّا
“And I will withdraw from you and what you call on besides Allah, and I will call upon my Lord; maybe I shall not remain unblessed in calling upon my Lord.” (19:48).
فَلَمَّا اعْتَزَلَهُمْ وَمَا يَعْبُدُونَ مِنْ دُونِ اللَّهِ وَهَبْنَا لَهُ إِسْحَاقَ وَيَعْقُوبَ ۖ وَكُلًّا جَعَلْنَا نَبِيًّا
“So when he withdrew from them and what they worshipped besides Allah, We gave to him Ishaq and Yaqoub, and each one of them We made a prophet.” (19:49).
 See Qur’an, Sura Qasas, Ayat 21-22.
فَخَرَجَ مِنْهَا خَائِفًا يَتَرَقَّبُ ۖ قَالَ رَبِّ نَجِّنِي مِنَ الْقَوْمِ الظَّالِمِينَ
“So he [Musa – Moses] went forth therefrom, fearing, awaiting, (and) he said: My Lord! deliver me from the unjust people.” (28:21).
وَلَمَّا تَوَجَّهَ تِلْقَاءَ مَدْيَنَ قَالَ عَسَىٰ رَبِّي أَنْ يَهْدِيَنِي سَوَاءَ السَّبِيلِ
“And when he [Musa – Moses] turned his face towards Madyan, he said: Maybe my Lord will guide me in the right path.” (28:22).
 See Qur’an, Sura Nisa, Ayat 157:
وَقَوْلِهِمْ إِنَّا قَتَلْنَا الْمَسِيحَ عِيسَى ابْنَ مَرْيَمَ رَسُولَ اللَّهِ وَمَا قَتَلُوهُ وَمَا صَلَبُوهُ وَلَٰكِنْ شُبِّهَ لَهُمْ ۚ وَإِنَّ الَّذِينَ اخْتَلَفُوا فِيهِ لَفِي شَكٍّ مِنْهُ ۚ مَا لَهُمْ بِهِ مِنْ عِلْمٍ إِلَّا اتِّبَاعَ الظَّنِّ ۚ وَمَا قَتَلُوهُ يَقِينًا
“And their saying: Surely we have killed the Messiah, Isa son of Marium, the messenger of Allah; and they did not kill him nor did they crucify him, but it appeared to them so (like Isa) and most surely those who differ therein are only in a doubt about it; they have no knowledge respecting it, but only follow a conjecture, and they killed him not for sure.” (4:157).
 Al Kafi Vol. 1 Pg.340; Ghaybah, Nomani Pg. 180.
 Kamaaluddin Vol.1. Pg.303
 Ghaybah, Tusi Pg.292, Kamaaluddin VoL2. Pg.485.
 Ghaybah, al-Toosi Pg.166 & 337. Al Kafi vol.1 Pg.336. Kamaaluddin vol.2 Pg.359 and 360. Kifayatul Asar Pg.264-265.
 Kamaaluddin vol.2 Pg.361. Kifayatul Asar Pg.265-266.
 Al Ihtejaj vol.2 Pg.602.