Musannaf Ibn Abi Shaybah

Hazrat Saeed bin Al-Musayyib narrates: The Messenger of Allah (peace and blessings be upon him) wrote letters to Kisra, Caesar, and Najashi. After praise, he said: "Come to a word that is common between us and you (and that is) that we worship none but Allah, and that we associate nothing with Him, and that we do not take one another as lords instead of Allah." But if they turn away, then say: "Bear witness that we are Muslims." Hazrat Saeed bin Al-Musayyib narrates: Kisra tore up the letter and did not even look at it. The Noble Prophet (peace and blessings be upon him) said: He himself is torn apart, and his nation is also torn apart. And Najashi accepted faith, and those who were with him also accepted faith. And he sent a pair of garments as a gift to the Messenger of Allah (peace and blessings be upon him). The Messenger of Allah (peace and blessings be upon him) said: As long as they leave you alone, you also leave them alone. And Caesar read the letter of the Messenger of Allah (peace and blessings be upon him) and said: After the letter of Prophet Sulaiman, I have not heard of any letter beginning with "Bismillah-ir-Rahman-ir-Raheem." Then he sent a messenger to Abu Sufyan and Mughirah bin Shu'bah. Both of them were present in the land of Caesar as traders. Caesar asked them about some conditions of the Messenger of Allah (peace and blessings be upon him). And he asked them: Who are the followers of this man? They replied: The weak and the women follow him. Then he asked: Tell me, have those who went to him ever returned? They replied: No! Caesar said: This man is a Prophet. Surely, he will gain dominance over the land beneath my feet. If I were with him, I would have kissed his feet.