Sayyiduna Amr bin Awf (may Allah be pleased with him) narrates: I heard the Prophet (peace and blessings be upon him) say: "The Hour will not be established until there is a garrison of the Muslims at a place called Bulan. O Ali!" The narrator al-Muzani says: This refers to Sayyiduna Ali bin Abi Talib (may Allah be pleased with him). He said: "Here I am, O Messenger of Allah." The Prophet (peace and blessings be upon him) said: "Know that you will soon fight Banu al-Asfar (the Romans), and the believers after you will fight them. Then some of the Muslims, from the people of the Hijaz, will go out against them; they will be people who strive in the way of Allah, and the blame of any blamer will not take hold of them concerning Allah, until Allah Almighty conquers Constantinople and Rome for them, which will be by glorifying Allah (tasbih) and declaring His greatness (takbir). They will demolish the fortresses of both places and obtain a great deal of wealth, the like of which they had never obtained before, so much that they will divide it by the shieldful. Then someone will cry out: 'O people of Islam, the Dajjal has emerged in your lands and among your families.' The people will leave the wealth; some will take it and some will leave it, and the one who takes it will regret it and the one who leaves it will also regret it. Then they will say: 'Who is this person crying out?' and they will not know who he is. Then they will say: 'Send a scout to Ludd; if the Dajjal has emerged, he will bring you news of him.' They will go and look, but they will not see anything, and they will see the people quiet. They will say: 'The one who cried out only cried out at us. So be resolute and remain rightly guided. Let us all go out to Ludd; if the Dajjal is there, we will fight him until Allah Almighty judges between us and him, and He is the best of judges. And if the situation is otherwise, it is your land, your families and your armies; you will return to them.'" (Allamah al-Haythami says:) I say:
Ibn Majah recorded this narration in abridged form.
Al-Tabarani recorded it. Its chain contains a narrator, Kathir bin Abdullah, whom the majority have declared da'if (weak), while al-Tirmidhi declared his narration hasan (good).