Are there any documentary Hadith-sources about the birth of Imam Mahdi from the Viewpoint of Sunni Scholars or not? 

Are there any documentary Hadith-sources about the birth of Imam Mahdi from the Viewpoint of Sunni Scholars or not? 

Due to the widely related and authentic traditions narrated from the Prophet, all Islamic scholars, whether Shiite or Sunni, are unanimous in believing that Imam Mahdi will indeed appear, reform the world and destroy all forms of oppression. Hence, all Muslims have faith in it and consider it to be an inseparable part of their religion.

Yet, All Shiite scholars, without any exception, believe that Imam Mahdi has already been born and is living in the present time. But, many Sunni scholars say that he shall be born in the future. However, some of them have related the event of the birth of Imam Mahdi in their books.
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