The Promised Deliverer (Kitab Al-Mahdi)
Dawud :: Book 36 : Hadith 4271
Narrated Umm Salamah, Ummul Mu'minin:
The Prophet (peace_be_upon_him) said: The Mahdi will be of my family, of the descendants of Fatimah. Abdullah ibn Ja'far said: I heard AbulMalih praising Ali ibn Nufayl and describing his good qualities.