Volume 7, Book 72, Number 764:
Narrated Anas bin Malik:
When the Prophet intended to write to the Byzantines, it was said to him, “Those people do not
read your letter unless it is stamped.” So the Prophet took a silver ring and got ‘Muhammad, the
Apostle of Allah’ engraved on it …. as if I am now looking at its glitter in his hand.