Narrated Anas:
When the Prophet (ﷺ) intended to write a letter to the ruler of the Byzantines, he was told that those people did not read any letter unless it was stamped with a seal. So, the Prophet (ﷺ) got a silver ring-- as if I were just looking at its white glitter on his hand ---- and stamped on it the expression "Muhammad, Apostle of Allah".
Reference | : Sahih al-Bukhari 2938 |
In-book reference | : Book 56, Hadith 151 |
USC-MSA web (English) reference | : Vol. 4, Book 52, Hadith 189 |
(deprecated numbering scheme) |