Abu Hurairah reported,
The Messenger of Allah ﷺ said, "The Hour will not come until the Romans descend at al-Amaq or at Dabiq. An army from Madinah, made up of the best people on earth at that time, will go out to meet them. When the two armies face each other, the Romans will say, 'Step aside and let us fight those of our people who were taken captive.' The Muslims will reply, 'No, by Allah, we will never let you stand against our brothers.' So they will fight them.A third of the Muslim army will be defeated, and Allah will never accept their repentance. A third will be killed, and they are the most excellent of martyrs in the sight of Allah. The remaining third will achieve victory, and they will never be tested with tribulation again. They will conquer Constantinople.While they are dividing the spoils, having hung their swords on the olive trees, Satan will cry out among them, 'The Antichrist has taken your place among your families!' So they will rush out, though it is a lie. When they reach Syria, the Antichrist will indeed appear.While they are preparing for battle and straightening the ranks, the call to prayer will be made, and Isa son of Maryam ﷺ will descend and lead them. When the enemy of Allah sees him, he will dissolve as salt dissolves in water. If he were left alone, he would melt away until he perished, but Allah will kill him by Isa's hand, and Isa will show them his blood on his spear."
Azami 15981
Sahihعن أبي هريرة
أن رسول الله ﷺ قال: لا تقوم الساعة حتى ينزل الروم بالأعماق أم بدابق، فيخرج إليهم جيش من المدينة من خيار أهل الأرض يومئذ، فإذا تصادفوا قالت الروم: خلوا بيننا وبين الذين سبوا منا نقاتلهم، فيقول المسلمون: لا والله لا نخلي بينكم وبين إخواننا، فيقاتلونهم، فينهزم ثلث لا يتوب الله عليهم أبدا، ويقتل ثلثهم، أفضل الشهداء عند الله، ويفتتح الثلث، لا يفتنون أبدا، فيفتتحون قسطنطينية، فبينما هم قتسمون الغنائم، قد علقوا سيوفهم بالزيتون، إذ صاح فيهم الشيطان: إن المسيح قد خلفكم في أهليكم، فيخرجون، وذلك باطل، فإذا جاؤوا الشام خرج، فبينما هم يعدون للقتال، يسوون الصفوف، إذ أقيمت الصلاة، فينزل عيسى ابن مريم ﷺ، فأمهم، فإذا رآه عدو الله ذاب كما يذوب الملح في الماء، فلو تركه لانذاب حتى يهلك، ولكن يقتله الله بيده، فيريهم دمه في حربته.
Muslim narrated it in the Book of Tribulations (2897) via Zuhayr bin Harb, who said, Mualla bin Mansur told us, Sulayman bin Bilal told us, Suhayl told us, from his father, from Abu Hurairah, and he related it.As for what is narrated from Muaz bin Jabal, who said, the Messenger of Allah 
said, "The flourishing of Bayt al-Maqdis means the ruin of Yathrib, the ruin of Yathrib means the outbreak of the great battle, the outbreak of the great battle means the conquest of Constantinople, and the conquest of Constantinople means the emergence of Dajjal," its chain is not sound. Abu Dawud (4294) and Tahawi in Sharh Mushkil (519-520) both narrated it via Abdul-Rahman bin Thabit bin Thawban, from his father, from Makhul, from Jubayr bin Nufayr, from Malik bin Yakhamir, from Muaz bin Jabal, and he related it. Abdul-Rahman bin Thabit bin Thawban has been criticized, and in my view his hadith is hasan so long as he does not bring something objectionable or narrate alone something with no basis, and he has narrated this hadith alone, and his sole narration cannot be relied upon for something like this. For this reason Dhahabi counted it among his objectionable narrations. There is also disagreement about its chain, part of which Daraqutni set out in Al-Ilal (53/6).Likewise, what is narrated from Muaz bin Jabal, who said, the Messenger of Allah said, "The great battle, the conquest of Constantinople, and the emergence of Dajjal will be within seven months," is not sound. Abu Dawud (4295), Tirmidhi (2238), Ibn Majah (4092), and Ahmad (22045) all narrated it through various routes from Abu Bakr bin Abu Maryam, from Walid bin Sufyan Ghassani, from Yazid bin Qutayb Sakuni, from Abu Bahriya, from Muaz bin Jabal, and he related it. Tirmidhi said, "This is a gharib hadith, we do not know it except through this route." And it is as he said, for he judged it gharib because only weak and unknown narrators transmitted it alone. Yazid bin Qutayb Sakuni was not deemed reliable by anyone other than Ibn Hibban, which is why Ibn Hajar described him as "acceptable," meaning when corroborated, and he was not corroborated. Walid bin Sufyan is unknown, and Abu Bakr bin Abu Maryam is Abu Bakr bin Abdullah bin Abu Maryam, who is daif.Likewise, what is narrated from Abdullah bin Busr, that the Messenger of Allah said, "Between the great battle and the conquest of Madinah there are six years, and the false messiah, Dajjal, will emerge in the seventh," is not sound. Abu Dawud (4296) and Ahmad (17691) both narrated it from Haywa bin Shurayh Himsi, who said, Baqiyya told us, from Buhayr, from Khalid, from Ibn Abu Bilal, from Abdullah bin Busr, and he related it. Ibn Majah (4093) narrated it from Suwayd bin Saeed, who said, Baqiyya told us, from Buhayr bin Saad, from Khalid bin Madan, from Ibn Abu Bilal, from Abdullah bin Busr, and he related it.In Ibn Majah's version it appears as "Khalid bin Abu Bilal," which is a mistake, as Mizzi stated in Al-Tuhfa (294/4), and the correct form is what appears in the narrations of Abu Dawud and Ahmad. This Ibn Abu Bilal's name is Abdullah, and no narrator is known to have transmitted from him other than Khalid bin Madan, and no one deemed him reliable other than Ibn Hibban. This is why Ibn Hajar said of him in Al-Taqrib, "acceptable," meaning when corroborated, and he was not corroborated in this narration.This poses a difficulty alongside the hadith of Muaz bin Jabal mentioned before it, and Abu Dawud affirmed decisively that this hadith is sounder than the hadith of Muaz.