The Black Banners the Ottoman Empire Imam al Mahdi and the Return of the Khalifate

And Ibn Abi Shaybah, Nu'aym ibn Hammad in al-Fitan, Ibn Majah and Abu Nu'aym narrated from
Ibn Mas'ud [radhiyallahu 'anhu] that he said:
"Once we were with the Messenger of Allah [sallallahu 'alayhi wa-sallam], when a group of youths from
Banu Hashim approached. When the Prophet [sallallahu 'alayhi wa-sallam] saw them, his eyes filled with
tears and his colour changed.
He [i.e. Ibn Mas'ud] said: "I said: "We see in your face something that worries us." So he said:
"We, the Ahl al-Bayt, are a people for whom Allah has chosen the hereafter over this world. And my household after me will face trials, banishment and pursuit, until a people from the east come with black banners, and they will ask for what is due, but not be given it. So they will fight and be victorious, and be given what they asked for. But they will not accept it from them until they hand it over to a man from myhousehold, who will fill it [i.e. the earth] with equity, as they had filled it with tyranny. So whoever among
you reaches that time, then let him go to them, even if he must crawl over ice, for he is the Mahdi."

And Ibn Majah, al-Hakim and Abu Nu'aym narrated from Thawban [radhiyallahu 'anhu] that he said:"The Messenger of Allah [sallallahu 'alayhi wa-sallam]:
"Three will fight where your treasure is, each one the son of a khalifah. But it will not go to a single one of them. Then, the black banners will come out of the east and kill you as no people have ever been killed.
Then, the khilafah of Allah, the Mahdi, will come, so when you hear of him then go to him and give thebay'ah to him, even if you must crawl over ice. For he is Allah's khalifah, the Mahdi."

And Ahmad, Nu'aym ibn Hammad, al-Hakim and Abu Nu'aym narrated from Thawban [radhiyallahu'anhu] that he said: "The Messenger of Allah [sallallahu 'alayhi wa-sallam] said:
"When you see the black banners have come forward from Khurasan, then go to them even if you have tocrawl over ice, for among them is Allah's khalifah, the Mahdi."

And al-Hasan ibn Sufyan and Abu Nu'aym narrated from Thawban [radhiyallahu 'anhu] that he said:"The Messenger of Allah [sallallahu 'alayhi wa-sallam] said:
"The black banners will come from the east, with hearts like iron bars. So whoever hears of them, let himgo to them and give them bay'ah, even if he must crawl over ice."