"Mahdi is one of us, the people of the Household. Allah will rectify him in a single night."
Sunan Ibn Majah Book 36, Hadith 160
← Previous Hadith "Three will fight one another for your treasure, each one of them the son of a caliph, but none of them will gain it. Then the black banners will come from the east, and they will kill you in an unprecedented manner." Then he mentioned something that I do not remember, then he said: "When you see them, then pledge your allegiance to them even if you have to crawl over the snow, for that is the caliph of Allah, Mahdi."

Sunan Ibn Majah Book 36, Hadith 159 Next Hadith → "We were with Umm Salamah and we were discussing Mahdi. She said: 'I heard the Messenger of Allah (ﷺ) say: "Mahdi will be one of the descendents of Fatimah."

Sunan Ibn Majah Book 36, Hadith 161