The matter of saviour and reformer has been discussed under different names, in religions and ideologies, and numerous writings exist, in this regard, with different explanations.
In the holy Qur’an too, numerous verses substantiate this point, a few of theme were pointed out while replying to the preceding queries. In the Sunni books, discussions can be found about Mahdaviyat and the promised Mahdi. Numerous traditions have been narrated in books on Hadith, as well as, the ‘Sihah’. Considering the importance of this subject, exclusive books too have been compiled on this subject. An accurate look into these traditions will lead a researcher to believe that the Mahdi is a known and specific figure with known characteristics.
Amongst the traditions narrated from the holy Prophet (that has come down in Sihah and other Sunni books), we set forth the following:
The holy Prophet said:
“The world would not terminate until a man from my progeny (whose name is the same as my name) would rule over the Arabs, and would become the king.” 
“Mahdi lives amongst my nation……To the one who shall ask from him something, he would bestow him so much wealth that he wouldn’t be able to take it away.” 
“Allah shall appoint someone from my progeny, who will fill the earth with equity and justice, just as it has been filled with injustice and tyranny.” 
“Mahdi is from the progeny of Fatemah.”
“Mahdi possesses a broad forehead and a slender nose.” 
“The son of Maryam shall descend with the Imam from you.” 
“Mahdi is from our progeny. Allah shall set right his affairs in one night.” 
The inhabitants of the earth and heavens shall turn pleased with Mahdi and during his rule, neither the earth shall withhold its treasures nor the sky its rain.”