The Sunni hadith on the Subject of the Mahdi
Dr. Fahimi: Mr. Hoshyar! Our friends know it. But let me tell you that I follow the Sunni school of thought. Hence the positive evaluation that you have of the Shia hadith-reports I do not share. In all likelihood extremist Shi’s for whatever reasons after having accepted the narratives about the Mahdiism must have fabricated traditions in support of their views and ascribed them to the Prophet. The evidence for my contention is that the traditions about the Mahdi are recorded only in your Shia books. There is no trace of these in our authentic --Sihah-- compilations. Yes I am aware that there are some traditions on the subject in our less reliable compilations. 
Mr. Hoshyar: In spite of the most unfavorable conditions under the Umayyads and the Abbasids whose politics and oppressive governments did not allow the discussion or the spread of hadith about Wilayat and Imamate and the Ahl-ul-Bayt or their being recorded in the books of the hadith your compilations of hadith are not completely void of any traditions on the subject of the Mahdi. If you are not tired I may cite some of them for you.
Engineer Madani: Mr. Hoshyar! Please continue your conversation.
Mr. Hoshyar: Dr. Fahimi! In your compilations the Sihah there are chapters devoted to the subject of the Mahdi in which traditions from the Prophet have been recorded. For example the following:
Abd Allah reports from the Prophet who said: "The world will not come to pass until a man from among my family whose name will be my name rules over the Arabs."
Tirmidhi has recorded this hadith in his Sahih  and comments: "This hadith on the Mahdi is reliable and has been related by Ali bin Abi Talib Abu Sa’id Umm Salma and Abu Hurayra":
Ali bin Abi Talib has narrated from the Prophet who said: "Even if there remains only a day on earth God will bring forth a man from my progeny so that he will fill the earth with justice and equity as it is filled with tyranny."
In another hadith Umm Salma narrates that she heard the Prophet say: "The promised Mahdi will be among my progeny among the descendants of Fatimah."
Abu Sa’id al-Khudari says: The Prophet said: "Our Mahdi will have a broad forehead and a pointed nose. He will fill the earth with justice as it is filled with injustice and tyranny. He will rule for seven years." 
Ali bin Abi Talib has related a tradition from the Prophet who informed him:
The promised Mahdi will be among my family. God will make the provisions for his emergence within a single night. 
Abu Sa’id al-Khudari has related a tradition from the Prophet who declared:
The earth will be filled with injustice and corruption. At that time a man from among my progeny will rise and will rule for seven or nine years and will fill the earth with justice and equity. 
Greater detail is provided in another hadith reported by Abu Sa’id al-Khudari. In this tradition the Prophet said:
Severe calamity from the direction of their ruler will befall my people during the Last Days. It will be a calamity which in severity shall be unprecedented. It will be so violent that the earth with injustice and corruption will shrivel for its inhabitants. The believers will not find refuge from oppression. At that time God will send a man from my family to fill the earth with justice and equity just as it is filled with injustice and tyranny. The dwellers of the heavens and the earth will be pleased with him. The earth will bring forth all that grows for him and the heavens will pour down rains in abundance. He will live among the people for seven or nine years. From all the good that God will bestow on the inhabitants of the earth the dead will wish to come to life again."
There are numerous traditions that convey these meanings in your books. I believe we have cited enough reports to make our point.
Note: This time we will work on just ten parts of this useful book but as always accompany us for other parts of this book in future.
(13). Hasan Sa’d Muhammad al-Mahdiyya fi al-islam (Cairo 1373) p. 69; Ibn Khaldun al-Muqaddima (Cairo edition) p. 311.
(14). Sahih Vol. 9 p. 74; also see: Shaykh Sulayman Yanabi’ al-mawadda (1308 AH edition) Vol. 2 p. 180; Muhammad b. Yusuf al-Shafi’i al-Bayan fi akhbar sahib al-zaman (Najaf edition) p. 57; and other Sunni sources.
(15). Abu Dawud Sahih Vol. 5/207; see also all the sources mentioned in note s 2. In addition see: Shablanji Nur al-absar p. 156; Ibn Hajar al-Sawa’iq al-muharriqah p. 161; Ibn Sabbagh Fusul al-muhimma p. 275; al-Saban As’af al-raghibin.
(16). Abu Dawud Sahih Vol. 2 p. 207; Ibn Majah Sahih Vol. 2 p. 519 and the sources mentioned in note s 3.
(17). Abu Dawud Sahih Vol. 2 p. 208; Fusul al-muhimma p. 275; and numerous other Sunni sources.
(18). Ibn Majah Sahih Vol. 2 p. 519. Also Ibn Hajar al-Sawa’iq al-muharriqa p. 161.
(19). Ahmad b. Hanbal Musnad Vol. 3 p. 27.
(20). Ibn Hajar al-Sawa’iq al-muharriqa p. 161; Yanabi’ al-mawadda Vol. 2 p. 177.
Source: The book named The Just Leader of Humanity
By Ayatullah Ibrahim AminiTranslated by: Dr. Abdulaziz Sachedina
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Some Ways for Waiving the Remaining Time of Occulation (Part 2)
Some Ways for Waiving the Remaining Time of Occulation (Part 3)
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The Badaa and its significance (Part 2)