Majma al-Zawaid — Hadith 12540

Sayyiduna Amr bin Awf (may Allah be pleased with him) narrates that the Prophet (peace and blessings be upon him) said: "The world will not come to an end until the Muslims have a garrison post at a place called 'Bulan', until they fight the Banu al-Asfar (the Romans). They will strive in the path of Allah, and the blame of any blamer will not hold them back concerning Allah, until Allah Almighty conquers Constantinople and Rome for them, which will be by means of tasbih and takbir (glorifying and magnifying Allah). The fort there will be demolished, and they will divide the wealth by placing it in shields." The Prophet (peace and blessings be upon him) said: "Then a caller will cry out: 'O people of Islam! The Dajjal has emerged in your lands and in your cities.' They will say: 'Who is this caller?' They will not know who he is. Then they will send someone ahead to look into whether the Dajjal has come. Those who went ahead will come back and say: 'We did not see anything, and we did not hear of it.' They will say: 'By Allah! This caller must have cried out from the sky or from the earth. Come, let us all go out. If the Dajjal has emerged, we will fight him until Allah Almighty judges between us and him, and He is the best of judges. And if it turns out otherwise, then they are your lands, your armies are there and your clans are there, and you will return to them.'" (Allamah al-Haythami says:) I say: Ibn Majah recorded it in abridged form.
Al-Bazzar recorded it. Its chain contains Kathir bin Abdullah, whom the majority declared da'if (weak), while al-Tirmidhi declared his hadith hasan (good).