Existence of Imam Mahdi (as) is widely acknowledged
Muhammad b. Jafar narrates that we disclosed our difficulties to Maalik b. Anas. He told us to bear patiently until the implementation of the verse,
“And We intend that those who have been rendered weak in the earth to make them the Imams and to make them the heirs” is manifested.

Naseel b. Zuhair recounts on the authority of Zaid b. Mataa, ‘The person whose reappearance is eagerly awaited by the people shall rise from the progeny of Imam Husain ibn Ali (a.s.).’

(Kitabul Ghaybah of Shaykh Tusi, vol.2, p. 115)

Muhammad b. Abdul Rahman b. Abi Layla reveals, ‘By Allah, Mahdi shall not be born, except from the progeny of Imam Husain (a.s.).’

(Ibid.)

EVERYONE WAS AWAITING MAHDI’S REAPPEARANCE

From the beginning of the Islamic era, the belief in Mahdi was so firmly entrenched in the hearts and minds of the people, that they fervently awaited his reappearance. The belief in his government of truth and equity was firmly instilled in their psyche. This belief gained further prominence among the masses as a result of the tumult and anguish under the oppressive regimes of the Bani Ummayyah and Bani Abbas caliphs.

One indicator of how strongly this belief was ingrained in the hearts of the people is that so many people either claimed the title of Mahdi for themselves, or were attributed with this title by their over-enthusiastic followers.

MUHAMMAD B. HANAFIYYA

He was the son of Ameerul Mo’mineen (a.s.). The people attributed him with the title of Mahdi, since his name was Muhammad, i.e. same as that of the Prophet (s.a.w.s.), and according to traditions Mahdi’s name and agnomen (kuniyyat) will be the same as that of the Prophet (s.a.w.s.). But a scrutiny of the events of his life reveals that he never claimed to be the Mahdi, but was ascribed with this title. However, it is possible that he remained silent and did not refute this attribution in the hope that the killing of Imam Husain (a.s.) and the other martyrs at Karbala could be avenged, and the Islamic government could return to its true inheritors.

Muhammad b. Sa’ad narrates that Muhammad b. Hanafiyya declared to the people, ‘Know that the government of the Ahle Haqq (People of Truth) is certain. It will be established whenever Allah wishes. Then whoever is alive to witness this kingdom has been favoured by Allah with good fortune, and one who dies before it will attain unlimited bounties of Allah.’

(Al Tabaqaatul Kubra, vol. 7, part 1, p. 71)

Muhammad b. Sa’ad further mentions that Muhammad b. Hanafiyya in one of his sermons to his 7,000 followers asserted, ‘You all act in haste in this affair (of establishing government). But by Allah there will be such people in your generations who will wage war for the rights of the Ahle Bayt (a.s.). The government of Ahle Bayt (a.s.) is certain, although there may be some delay in establishing it. I swear by the One in whose hand lies Muhammad’s life that dominion will return to the family of Prophethood’.

(Ibid. p. 70)

2. MUHAMMAD IBN ABDULLAH IBN HASAN

A section of Muslims considers Muhammad Ibn Abdullah Ibn Hasan to be the Mahdi. Abul Faraj writes:
Hameed Ibn Saeed narrates that people rejoiced at the birth of Muhammad Ibn Abdullah. The reason being that they were narrating from the Holy Prophet (s.a.w.s.) that the name of Mahdi will be Muhammad. Therefore, they hoped that Muhammad is the Promised Mahdi. He became the cynosure of all eyes and everyone’s favourite. He became the centre of discussion in gatherings and public places and the Shias gave glad tidings to each other for him.
(Maqaatelut Taalebeen, p. 165)

At another place Abul Faraj writes: When Muhammad b. Abdullah was born his relatives named him as Mahdi, as they thought that he was the ‘Promised Mahdi’ whose advent was prophesied in traditions. But the knowledgeable ulema among the sons of Abu Talib knew him as ‘Nafse Zakiyyah’ (pure soul) about whom it was destined that he would be martyred in ‘Zaitul Hejaar’.

(Maqaatelut Taalebeen, p. 157)

THE JURISTS OF MADINA AND TRADITIONS REGARDING MAHDI

Abul Faraj records: When Muhammad b. Abdullah b. Hasan revolted, he received support from Muhammad b. Ajalaani, a jurist of Madina. When Muhammad b. Abdullah was killed, the ruler of Madina, Jafar b. Sulaymaan summoned Muhammad b. Ajalaani and asked, ‘Why did you revolt with the liar?’ Then he ordered that his hands should be severed as penalty for his revolt. But the jurists and elders of Madina interceded on behalf of Muhammad b. Ajalaani thus, ‘O Emir, Muhammad b. Ajalaani is a jurist and a pious man, we hope you will pardon him. He mistook Muhammad b. Abdullah to be the Promised Mahdi prophesied in traditions.’
(Ibid. p. 193)

Abul Faraj further writes, ‘When Muhammad b. Abdullah rose in rebellion, Abdullah b. Jafar, a scholar, jurist, and a man of traditions (Muhaddith), also supported him. But when Muhammad b. Abdullah was killed, Abdullah b. Jafar fled, and remained in hiding until he was assured pardon.’

One day Jafar b. Sulayman, the ruler of Madina came to him and addressed him thus, ‘Despite your knowledge, jurisprudence, understanding and wisdom, why did you rise with Muhammad b. Abdullah?

Abdullah b. Jafar replied, ‘My association with Muhammad b. Abdullah was due to the fact that I took him to be the ‘Promised Mahdi’, on the basis of traditions which has reached us. I did not doubt him till he was killed, which is when I realised my mistake. After this I shall never repeat such an error.’
(Ibid. p. 195)

The incidents outlined above highlight the fact that the belief in Mahdaviyat was acknowledged by Muslims from the time of the Holy Prophet (s.a.w.s.), and was not an innovation in religion. People in all ages were awaiting the appearance of this Mahdi, prophesied by the Holy Prophet (s.a.w.s.). That is why we have seen that in various ages, the oppressed who were unaware of the signs of the true Mahdi, mistook personalities like Muhammad b. Hanafiyyah, Muhammad b. Abdullah b. Hasan among others, for the Mahdi. But the Shias who were familiar with the traditions of the Ahle Bayt (a.s.), and Muhammad b. Abdullah himself, were aware of the promised Mahdi’s identity.

Abul Faraj writes: A person asked Abdullah b. Hasan, ‘When will Muhammad rise?’ Abdullah replied, ‘He will rise only after I get killed. But even he will be killed.’ Then that person declared, ‘We are from Allah and unto Him shall we return. If Muhammad is killed, the entire nation will be destroyed!’ Abdullah replied, ‘That will never happen.’
The person queried once again, ‘When will Ibrahim rise?’ Abdullah replied, ‘He shall not rise until I am slain. But even he will be killed.’ The person declared once again, ‘We are from Allah and unto Him shall we return. If Ibrahim is killed, the nation will be destroyed.’ Abdullah replied, ‘No that will never happen. Their master, the Promised Mahdi, will rise as a twenty-five year old youth. He will decimate the enemies.’
(Ibid. p. 166)

Abul Faraje Isfahani records that Abul Abbas informed Marwan that Muhammad claimed to be the Mahdi. Marwan replied, ‘Neither is he the Mahdi nor anyone else from his father’s progeny. On the contrary, the promised Mahdi shall be the son of a slave-girl (of Allah).’

(Ibid. p.167)

(Quotes: WWW.Al Muntazar.net)