It is narrated from Sayyiduna Abu Tha'labah al-Khushani (may Allah be pleased with him), a Companion of the Prophet (peace and blessings be upon him), that he was in al-Fustat during the caliphate of Sayyiduna Mu'awiyah (may Allah be pleased with him), and Sayyiduna Mu'awiyah (may Allah be pleased with him) was preparing the people for the campaign against Constantinople. Sayyiduna Abu Tha'labah al-Khushani (may Allah be pleased with him) said: "By Allah, this Ummah will not be incapable of half a day. When you see Syria as the dining table of one man and his household, at that time Constantinople will be conquered." (Allamah al-Haythami says:) I say: Abu Dawud recorded part of this narration.
Ahmad recorded it, and its narrators are the narrators of the Sahih.