Sayyiduna Mustawrid (may Allah be pleased with him) says: I was with Sayyiduna Amr ibn al-As (may Allah be pleased with him), and I said to him that the Messenger of Allah (peace and blessings be upon him) said: "Your greatest opponents are the Romans; their end will be with the Day of Resurrection." Sayyiduna Amr (may Allah be pleased with him) said to this: "Did I not forbid you from narrating such ahadith?"