Imam Mahdi’s (as) Existence: An Accepted Fact
Abul Faraj writes: Whenever Jafar bin Mohammed (a.s.) used to see Mohammed ibn Abdullah, he used to cry and say:

“May my life be sacrificed for him (Mahdi a.t.f.s.), people think that this person is the Promised Mahdi, but he will soon be martyred. In the book of Ali (a.s.), he has not been included among the Caliphs of the people.”

(Maqaatil al-Taalebeen, p.142)

He further writes: A group was present near Mohammed bin Abdullah, when Jafar bin Mohammed (a.s.) arrived, and the people welcomed him with a lot of respect. Then Imam (a.s.) enquired about their conversation. They replied:
We have decided to pay allegiance to Mohammed bin Abdullah, who is the Promised Mahdi.’ Imam (a.s.) warned: ‘Refrain from this action, because the time of Mahdi’s appearance has not arrived, and Mohammed is not the Mahdi’.
(Ibid, p. 141)

DE’BAL’S COUPLET REGARDING MAHDI (A.T.F.S.)

De’bal, the poet of Ahle Bayt (a.s.) recited his famous couplets in the presence of Imam Reza (a.s.) and in the end, he recited the following verse:

“The reappearance of the Imam is certain and imminent
He will rise on Allah’s Name and (His) blessings.”

Hearing this, Imam Reza (a.s.) started weeping and exclaimed

‘(O De’bal) Ruhul Qudus has spoken through your tongue! Do you know that Imam?’ De’bal replied, ‘No. But I have heard that a person from your progeny will bring about a revolution, and will fill this earth with justice and equity. Imam (a.s.) prophesied, ‘After me, my son Mohammed (a.s.) will be the Imam, and after him, his son Ali (a.s.) will be the Imam and after Ali (a.s.) his son Hasan (a.s.) will gain Imamat. After Hasan (a.s.), his son Hujjat, the Qaem (a.t.f.s.), shall gain this prestigious station. He shall be in occultation and awaiting his reappearance is necessary. And when he will reappear it is necessary to obey and follow him. He is the person who will fill the earth with justice and equity. The time of his reappearance is not fixed, and it is narrated by my forefathers that his reappearance will be sudden.’

(Yanaabi-ul-Mawaddah, vol. 2, p. 197)

These types of incidents and witnesses are found in many historical books. If one wants to know about this in detail he should refer to such books.

PSEUDO-MAHDIS

This is another subject, which only serves to establish the veracity and authenticity of Mahdaviyat. It is an accepted fact that from the beginning of Islam there have been several pseudo-Mahdis, both claimants as well as the ascribed ones. To make it sufficiently clear for the readers we have mentioned a few:

A group of Muslims considered Mohammed Ibn Hanafiya to be an Imam and the Mahdi. They claimed that he would disappear in a mountain named Razwa and would reappear from the same place and fill the earth with justice and equity.”
(Al Melal wa Nehal by Shahrastaani, vol. 2, p. 242, Feraqush Shia by Nawbakhti, p. 27)

A group of the Jaroodiya sect considers Mohammed bin Abdullah bin Hasan to be the Mahdi and await his reappearance.
(Al-Melal wa al-Nehal, vol. 1, p. 256, Feraqush Shia, p. 62)

The Naadoosiya sect took Imam Jafar-e-Sadiq (a.s.) to be the Mahdi. According to them, Imam Sadiq (a.s.) is alive and is in occultation.
(Al-Melal wa al-Nehal, vol. 1, p. 273,
Feraqush Shia, p. 67)

The Waaqefiyyah considered Imam Moosa bin Jafar (a.s.) to be alive and in occultation. They believed that after reappearing, Imam would fill the earth with justice and equity.
(Al-Melal wa al-Nehal, vol. 1, p. 278,
Feraqush Shia, p. 80-83)

The Ismaailis believe that Ismail bin Jafar al-Sadiq (a.s.) has not died, but due to dissimulation (taqaiyya), he is said to have died.
(Al-Melal wa al-Nehal, vol. 1, p. 279,
Feraqush Shia, p. 67)

The Baaqeriyah sect took Imam Baqir (a.s.) as the Promised Mahdi.

The Mohammadia sect believed that after Imam Ali Naqi (a.s.), his son Mohammed bin Ali, is the Imam and they considered him to be alive although he had died during his father’s time.

The Jawaaziyyah claimed that Hazrat Hujjat ibn al-Hasan has a son and he is the Promised Mahdi.
(Kitab Tanbeehat al-Jaleeyah fi Kashfe Asraaril Bateneeyah, by Mohammed Karim Khurasani, Najaf, 1351 A.H., p. 40-42)

A sect of the Haashemiyyah believe that Abdullah ibn Harbe Kindi is the Imam and considered him to be alive and in occultation. The members of this sect are awaiting his reappearance.
(Al-Melal wa al-Nehal, vol. 1, p. 245)

A group of Mubarakia considered Mohammed Ibn Ismail as the Imam who is alive and in occultation.
(Al-Mehal wa al-Nehal, vol. 1, p. 279)

The Yazidiya sect believed that Yazid (l.a.) had ascended to the skies, and would come back and fill the earth with justice and equity.
(Kitabul Yazidiya compiled by Saduqul al-Damluji, printed at Mosil, 1368 A.H., p. 167)

The Ismailias believed that those traditions, which had come for Mahdi actually pertain to Mohammed bin Abdullah who has the title of al-Mahdi and rules Egypt and the western countries. These people ascribe a false tradition to the Holy Prophet (s.a.w.s.), wherein he supposedly said,
‘In 300 years, the sun will rise from the west’.
(Tarikhe Rauzat al-Safa, Tehran, vol. 4, p. 181)

One of the groups of the Imamiya sect believed that Imam Hasan Askari (a.s.) was alive and was in fact the Qaim. They claimed that he was in occultation, and would reappear later to establish justice and equity on the earth. Another group was of the opinion that Imam Hasan Askari (a.s.) had already died but would be made alive once again, and bring the revolution, as Qaim means to stand after death.
(Al Melal wa al-Nehal, vol. 1, p. 284,
Feraqush Shia p. 96, 97)

The Qaraameta considered Mohammed bin Ismail to be the Promised Mahdi. They believed that he was alive and was living in a Roman kingdom.
(Kitabul Mahdiya fi al-Islam, p. 170, Feraqush Shia, p. 72)

The Abi Muslimiya sect considered Abu Muslim Khurasani to be the Imam and Qaim.
(Feraqush Shia, p. 47)

One group believed Imam Hasan Askari (a.s.) to be Mahdi. They claimed that after dying he had become alive once again and was currently living in occultation. He would reappear later and fill the earth with justice and equity.

The above mentioned names are of those people who were considered to be the promised Mahdi by their group of ignorant followers, years after the demise of the Holy Prophet (s.a.w.s.). But now most of those sects are extinct and are confined to books of history. From that era till the current one, we find many others from different cities who have introduced themselves as the promised Mahdi. Intense battles took place and a lot of blood was shed to establish their claims. Details of these conflicts can be found in the book ‘Mahdi Ibtedaa-e-Islam se Terhavi Sadi Tak’, ‘Al Mahdiya fi al-Islam’ and other historical books dealing with the topic of Mahdi.

FABRICATED TRADITIONS

It is indeed tragic that followers of the some of the claimants fabricated a large number of traditions to support the claims of their leaders. Later these fabricated traditions gradually found their way in the books of traditions. Therefore, even today, one can find numerous fabricated traditions that were coined to substantiate the claims of pseudo-Mahdis. The below-mentioned tradition is a good illustration of such fabricated traditions.

The Holy Prophet (s.a.w.s.) said:

“The world will not come to an end unless Allah sends a person from my Ahle Bayt whose name shall be the same as my name, and whose father’s name is akin to my father’s name. He will fill the earth with justice and equity as it would be fraught with injustice and oppression.”

(Fusulul Mohimmma, pg. 27)

In this tradition, the name of Mahdi’s father is supposedly the same as the name of Prophet’s (s.a.w.s.) father viz. Abdullah. This tradition contradicts many other authentic traditions in which the name of Imam’s (a.s.) father is said to be ‘Hasan’.

(Quotes: WWW.Al Muntazar.net)