Majma al-Zawaid — Hadith 12419

Sayyiduna Abu Umamah (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) said: "There will be four peace treaties between you and the Romans, and the fourth time the treaty will be with a man from the family of Heraclius, and it will last seven years. At that point a man from the tribe of Abd al-Qays, whose name is al-Mustawrid bin Khaylan, submitted: O Messenger of Allah! Who will be the leader of the people at that time? He said: A man from my descendants, who will be forty years old. His face will be like a shining star, there will be a black mole on his right cheek, he will be wearing two white cloaks, as though he were one of the men of Banu Isra'il. He will rule for twenty years; he will bring out the treasures and conquer the lands of the polytheists."
Al-Tabarani recorded it. Its chain contains Anbasah bin Abi Saghirah, who is da'if (weak).