Dhi Mukhbir bin Akhi Najashi reported,

He heard the Messenger of Allah ﷺ say, "You will make a secure peace treaty with the Romans, then you and they together will fight an enemy beyond them. You will be granted victory and take spoils, then you will withdraw and camp at a meadow with hillocks.There a man among the Romans will say, 'The Cross has prevailed,' and a man among the Muslims will reply, 'Rather, Allah has prevailed.' The Muslim will leap toward their cross, which is not far from him, and break it. The Romans will then turn on the one who broke their cross and strike off his neck. The Muslims will rush to their weapons and the two sides will fight, and Allah will honor that band of Muslims with martyrdom.The Romans will say to their commander, 'We have spared you the trouble of the Arabs,' and they will gather for the great battle. They will come against you under eighty banners, beneath each banner twelve thousand men."

Azami 15978

Sahih

عن ذي مخبر ابن أخي النجاشي

أنه سمع رسول الله ﷺ يقول: تصالحون الروم صلحا آمنا حتى تغزو أنتم وهم عدوا من ورائهم، فتنصرون وتغنمون، وتنصرفون حتى تنزلوا بمرج ذي تلول، فيقول قائل من الروم: غلب الصليب، ويقول قائل من المسلمين: بل الله غلب، فيثور المسلم إلى صليبهم، وهو منه غير بعيد، فيدته، وتشور الروم إلى كاسر صليبهم، فيضربون عنقه، ويثور المسلمون الى أسلحتهم، فيقتتلون، فيكرم الله تلك العصابة من المسلمين بالشهادة، فتقول الروم لصاحب الروم: كفيناك العرب، فيجتمعون للملحمة، فيأتونكم تحت ثمانين غاية، تحت كل غاية اثنا عشر ألفا.

الأعظمي 15978صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami al-Kamil
Book
Tribulations and signs of the Hour
Chapter
Minor signs of the Hour
Section
Among the signs of the Hour is that Muslims will fight the Romans, and Allah will grant them victory, and that will be at the end of time
Numbering
Jami al-Kamil 15978 (2nd edition)
Azami 15978