Majma al-Zawaid — Hadith 9587

Sayyiduna Dihyah al-Kalbi (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) sent me with a letter to Caesar, the ruler of Rome. I said (to his courtiers): "Seek permission for the (envoy of the) Messenger of Allah to enter." The doorkeeper went to Caesar, and he was told that at the door there was a person who claims that he is the envoy of the Messenger of Allah. They became alarmed at this. Caesar said: "Bring him to me." (Sayyiduna Dihyah (may Allah be pleased with him) says:) They took me to him, and with him were his patricians (religious scholars or priests). I gave him the letter and it was read before him, and in it was written: "In the name of Allah, the Most Gracious, the Most Merciful. This is from the Messenger of Allah to Caesar, the ruler of Rome." Then Caesar's nephew, who was of red complexion, blue-eyed and with straight hair, said: "Do not read this letter today, for he has begun the letter with his own name, and he has written you as the man in charge of Rome; he has not written the king of Rome." The narrator says: The letter was read until, when it was finished, Caesar gave orders concerning those people and they got up and left him. Then Caesar sent for me; I went to him, he asked me questions, and I answered him. Then he sent a message to a bishop and called him. He came to him; he was a man of prominent standing, the people gave weight to his opinion and preferred his word. When the letter was read, the bishop said: "By Allah! He is the very one about whom Sayyiduna Musa (peace be upon him) and Sayyiduna Isa (peace be upon him) gave us glad tidings, and for whom we were waiting." Caesar said: "Then what do you command me?" The bishop said: "I will affirm him and I will follow him." Caesar replied: "I know that it is so, but I cannot do it; in that case my kingdom would depart, and the Romans would kill me."
Tabarani recorded it. Its chain contains Yahya bin Abd al-Hamid al-Himmani, who is da'if (weak).