It was narrated that Anas said: “The Messenger of Allah صلی اللہ علیہ وآلہ وسلم wanted to write to the Romans, and they (the Companions) said: ‘They do not read any letter unless it has a seal.’ So he took a ring of silver and it is as if I can see its whiteness on his hand, and engraved on it (were the words): ‘Muhammad Rasul Allah. “ (Sahih)