It was narrated from Abu Hurairah that the Messenger of Allah (s.a.w.a.) said: “Even if there was only one day left of this world, Allah would make it last until a man from my household took possession of (the mountain of) Dailam and Constantinople.”
It was narrated that 'Abdullah said: "While we were with the Messenger of Allah (s.a.w.a.), some youngsters from Banu Hashim came along. When the Prophet (s.a.w.a.) saw them, his eyes filled with tears and his color changed. I said: 'We still see something in your face that we do not like (to see).' He said: 'We are members of a Household for whom Allah has chosen the Hereafter over this world. The people of my Household will face calamity, expulsion and exile after I am gone, until some people will come from the east carrying black banners. They will ask for something good but will not be given it. Then they will fight and will be victorious, then they will be given what they wanted, but they will not accept it and will give leadership to a man from my family. Then they will fill it with justice just as it was filled with injustice. Whoever among you lives to see that, let him go to them even if he has to crawl over snow.'"
It was narrated from 'Ali that the Messenger of Allah (s.a.w.a.) said: "Mahdi is one of us, the people of the Household. Allah will rectify him in a single night."