For We have written in the Psalms...
For We have written in the Psalms, after the remembrance, `My righteous servants will inherit the earth.' (21:105) Allah has promised those of you who believe and do righteous deeds that He will surely make you successors in the land just as He made those who were before them successors, and that He will surely establish their religion for them, and will give them in exchange, after their fear, security: `They shall serve Me, not associating with Me anything.' (24:55) It is He who has sent His Messenger with the religion of truth, that he may lift it above every religion, though the unbelievers be averse.
(61:9) We desire to be gracious to those who were abased in the land, and to make them leaders, and to make them the inheritors. (28:5) The above verses clearly show that in the end the world will fall into the hands of Allāh’s worthy and righteous servants and that they will become the leaders of the people of the world. Then Islam will be victorious over all religions.
Belief in the Mahdi & Sunni Authorities In this subject, the scholars in the Sunni school have related many hadiths from the Prophet of Islam through trustworthy narrators. From among them are ahadith which say that the Imams are twelve persons and that they are all from the Quraysh. Al-Mahdi, the promised one, is from the family of the Prophet and a descendent of Imam ‘Ali and Fatimah az-Zahra, and in many ahadith it is mentioned that he is from the line of Imam Husayn.
The Sunnis have mentioned and recorded hundreds of ahadith about the Mahdi in more than seventy books through their own authorities of which we shall just mention a few examples: Al-Musnad of Ahmad bin Hanbal (d. 241 AH). Sahih of al-Bukhāri (d. 256 AH). Sahih of al-Muslim (d. 261 AH). Sunan of Abu Dāwud as-Sajistāni (d. 275 AH). Sahih of at-Tirmidhi (d. 279 AH).
The authors of the above books are among the most authoritative books of the Sunnis and, more interestingly, all died either before the birth of the Twelfth Imam (255 AH) or shortly after his birth. The Hidden Reformer We have at least three hundred ahadith from the Prophet and from five Imams about Imam al-Mahdi (a.s.).