Anas reported
that when Allah's Apostle (ﷺ) decided to write to the Kisra (the King of Persia) , Caesar (Emperor of Rome) , and the Negus (the Emperor of Abyssinia) , it was said to him that they would not accept the letter without the seal over it ; so Allah's Messenger (ﷺ) got a seal made , the ring of which was made of silver and there was engraved on it : "Muhammad , the Messenger of Allah."