All of the Muslim sects are awaiting the coming of the Mahdi (‘a) without any exceptions. They also all believe that he will be from the family of the Prophet (ṣ).
All of the Muslim sects are awaiting the coming of the Mahdi (‘a) without any exceptions. They also all believe that he will be from the family of the Prophet (ṣ). This consensus in opinion exists to such a degree that even the most extreme of groups (such as the Wahhabis) also believe in this coming revolution. Not only have such groups accepted this belief, but they also defend it and consider it to be one of the foundational ideologies of Islam.
In any case, before showing the acknowledgement of a group of scholars from the Ahl al-Sunnah in this matter, it would first be beneficial to show what the Rābiṭah al-’Ālam al-Islāmī has had to say in regards to this matter. This is one of the most important religious centers of thought amongst the Wahhabis in Mecca. One of the reasons behind the importance of this statement is that it shows that on the one hand, the most extreme group in opposition to the Shiʿa (namely the Wahhābīs) have also accepted this belief. Not only have they accepted it, but they have also seriously defended it and consider it as being one of the established and definitive beliefs of Islam. In addition, this center is active on a worldwide scale.
In the year 1976, an individual by the name of Abū Muḥammad from Kenya, asked a question in regards to the appearance of the Mahdi al-Muntaẓar (‘a) from the ‘Rābiṭat al-’Ālam al-’Islāmī’ organization. The reply ended up coming from the head of the center. In his reply, he mentioned that Ibn Taymīyah (the founder of the Wahhābī sect) accepted the traditions in regards to the Mahdi (‘a), and also sent the man a short treatise, which five of the famous scholars of the Ḥijāz had prepared. In the treatise, after mentioning the name of Imam al-Mahdi (‘a) and the area of his appearance (Mecca), the following was written:
“…When corruption appears in the world and disbelief and oppression spread, Allah will fill the earth with justice and equity through means of him (the Mahdi (‘a)), much like it had been filled with oppression and tyranny.”
He is the last of the twelve just rulers, whom the Prophet (ṣ) has given news of (and which has been recorded in the Sihah books). Many of the companions of the Prophet (ṣ) have narrated such traditions from him (ṣ) These include individuals such as: ‘Uthmān ibn ‘Affān, ‘Ali ibn Abī Ṭālib (‘a), Ṭalḥah ibn ‘Ubaydullah, ‘Abd al-Raḥmān ibn ‘Awf, ‘Abdullah ibn ‘Abbās, ‘Ammār ibn Yāsir, ‘Abdullah ibn Mas’ūd, Abū Sa’īd al-Khudrī, Thawbān, Qurah ibn Āyās al-Muzanī, ‘Abdullah ibn Ḥārith, Abū Hurayrah, Hudhayfah ibn Yamān, Jābir ibn ‘Abdullah, Abū Amamah, Jābir ibn Mājid, ‘Abdullah ibn ‘Umar, Anas ibn Mālik, ‘Umrān ibn Ḥaṣīn, and Umm Salamah.
Then he adds: There are many traditions narrated by the Prophet (ṣ) and also the testimony of the companions (which hold the weight of traditions for them) and these are narrated in a great number of famous Islamic books and Islamic texts. These include the Sunans like that of Abī Dāwūd, al-Tirmidhī, Ibn Mājah and Ibn ‘Umar al-Dānī and the Masānīds like that of Aḥmad, Abī Ya’lā, al-Bazzāz and Ḥākim al-Nayshabūrī as well as Muʿjams like that of al-Ṭabrānī, al-Rawayānī, al-Dār al-Quṭnī, and Abū Naʿīm in the book ‘Akhbār al-Mahdi; Khatīb al-Baghdādī in his History of Baghdad, Ibn ‘Asākir in his History of Damascus, as well as other.
Then he adds: “Some amongst the Islamic scholars have compiled independent texts on this subject. These include: Abū Naʿīm’s book ‘Akhbār al-Mahdi, Ibn Ḥajar al-Haytamī’s Al-Qawl al-Mukhtasar fī ‘Alāmāt al-Mahdi al-Muntaẓar, al-Shawkānī’s al-Tawḍīḥ fī tawātur-i mā jā’ fī al-Muntaẓar-i wa al-Dajjāl-i wa al-Masīḥ, Idrīs al-‘Arāqī al-Maghribī’s al-Mahdi, Abū al-’Abbās ibn ‘Abd al-Mu’mīn al-Maghribī’s al-Wahm al-maknūn fī al-radd-i ‘Alā ibn Khaldūn.”
The last individual who has written a detailed discourse on this matter is the head of the Islamic University of Medina, who published these articles in several volumes of the universities journal.
“A number of great Islamic scholars, both in past times as well as current, have explained in their writings that the traditions on the Mahdi (‘a) are of Tawātur (highest rank of authenticity) and thus cannot be rejected. Amongst such scholars are: al-Sakhāwī in his book Fatḥ al-Mughīth, Muḥammad ibn Aḥmad al-Safāwīnī in his book Sharḥ al-ʿAqīdah, Abū al-Ḥasan al-Abrī in his Manāqib al-Shāfiʿī, Ibn Taymīyah in his fatwas, al-Suyūṭī in his al-Ḥāwī, Idrīs al-‘Arāqī al-Maghribī in the book that he wrote about the Mahdi (‘a), al-Shawkānī in his book al-Tawḍīḥ fī tawātur-i mā jā’ fī al-Muntaẓar-i wa al-Dajjāl-i wa al-Masīḥ …, Muḥammad ibn Ja’far al-Kattānī in his book Naẓm al-Mutanāthir fī ḥadīth al-mutawātir, and Abū al-’Abbās ibn ‘Abd al-Mu’mīn in his book al-Wahm al-Maknūn…
At the end of the statement, they have added: It is only Ibn Khaldūn who has sought to criticize the traditions regarding the Mahdi (‘a), through the use of fabricated and foundationless traditions. These traditions say that the Mahdi (‘a) is no one other than Jesus (‘a). Established Islamic scholars have refuted his words; in particular amongst these scholars is Ibn ‘Abd al-Mu’mīn, who has written a book refuting him, and this book was published about 30 years ago and can be found sold all over the world.
The Ḥāfiẓes of tradition, as well as the narrators of tradition have classified every single tradition about the Mahdi (‘a) as being either Ṣaḥīḥ or Ḥasan, however the entirety of the such traditions are undoubtedly Mutawātir and Ṣaḥīḥ. Therefore, the belief in the appearance of the Mahdi (‘a) is obligatory upon all Muslims, including the Ahl al-Sunnah; only a very small group of ignorant individuals have rejected this belief. By the head of the Islamic Fiqh Organization, Muḥammad Muntaṣir Kanānī.”
In addition to this statement, it is beneficial here to list some of the statements of other scholars from the Ahl al-Sunnah in regards to their belief in the Mahdi (‘a):
1- The famous scholar Shaykh Manṣūr ‘Alī al-Nāṣif, who is the author of the book al-Tāj has written the following: Amongst the past and present scholars, it is famously known with certainty, that at the end of time, a man by the name of al-Mahdi (‘a), from the family of the Prophet (ṣ) will appear. He will predominate over all of the Islamic countries. The Muslims will all become his followers; he will act with justice amongst them, and strengthen the religion. Then the Dajjāl shall appear. Jesus (‘a) will descend from the heavens and kill the Dajjāl, or he will participate in the killing of the Dajjāl with the Mahdi (‘a) … Many of the great companions and scholars have narrated the traditions of the Mahdi (‘a)… and Ibn Khaldūn has erred when he considered such traditions to be weak in their authenticity.
2- Even Ibn Khaldūn, who is famous in his opposition to the traditions in regards to the Mahdi (‘a) has not been able to reject the traditions related to this issue. He has said: During both past and present times, it has been famous amongst the Muslims that at the end of time, a man from the family of the Prophet (ṣ) will appear who will affirm the religion of Islam, he will manifest justice, and the Muslims will follow him.
3- Muḥammad al-Shablanjī, the famous Egyptian scholar, has written the following in his book, Nūr al-Abṣār: Mutawātir traditions have reached us showing that the Mahdi (‘a) is from his (the Holy Prophet’s (ṣ)) household, and that he will fill the earth with justice and equity.
4- Shaykh Muḥammad al-Ṣabbān has written the following in his text: Isʿāf al-Rāghibīn: Mutawātir traditions have been narrated from the Prophet (ṣ) stating that the Mahdi (‘a) (will in the end) revolt, and that he is from the family of the Prophet (ṣ), and he will fill the earth with justice and equity…
5- Ibn Ḥajr al-Asqalānī has narrated the following in his book al-Ṣawā’iq al-Muḥriqah from Abū al-Ḥasan al-Amrī: Numerous (Mutawātir) traditions have been narrated from the Prophet (ṣ) which state that in the end, the Mahdi (‘a) will appear and he will be from the Ahl al-Bayt of the Prophet (ṣ)… he will fill the earth with justice.
6- The writer of the book Al-Tāj, after mentioning the book of al-Shawkānī (the famous scholar of the Ahl al-Sunnah whose book is in regards to the traditions relating to the Mahdi (‘a), the Dajjāl, and the return of Jesus (‘a)) has said: What has been said should be sufficient for those who have the slightest shreds of faith and fairness.
For more details and information in regards to the traditions from the Ahl al-Sunnah about the great worldwide revolution, refer to the book Al-Mahdi and the book Muntakhab al-Athar fī Aḥwāl al-Imām al-Thānī ‘Ashar.
 The full Arabic text of this statement can be found in the book: Mahdi, The Great Revolutionary, from pages 151 to 155.  Al-Tāj, vol. 5, p. 310.  Ibn Khaldūn, Beirut Print, p. 311.  Nūr al-Absār, Cairo, Maktabah Mashhad al-Husaynī, p. 157: «تواترت الاخبار عن النّبى(صلى الله علیه وآله وسلم) على انّ المهدى من اهل بیته و انّه یملا الارض عدل»  As’āf al-Rāghibīn, in the footnotes section of Nūr al-‘Abṣār, p. 140.  Ṣawā’iq al-muḥriqah, p. 99.  Al-Tāj, vol. 5, p. 327: «هذا یکفى لمن کان عنده ذرّة من الایمان و قلیل من انصاف!»  Taken from the text: Ḥukūmat Jahānī Mahdi, Ayatollah Nasir Makarem Shirazi, Intishārāt Nasle Javān, Qum, 1390 Hijrī Shamsī, p. 133.