Narrated Anas bin Malik:
Once the Prophet (peace be upon him) wrote a letter or had an idea of writing a letter. The Prophet was told that they (rulers) would not read letters unless they were sealed. So the Prophet got a silver ring made with “Muhammad Allah’s Messenger” engraved on it. As if I were just observing its white glitter in the hand of the Prophet
(Bukhari Vol. 1, Book 3, Hadith 65)
