What was the engraving on the silver ring that Prophet Muhammad (saw) used when he intended to write to the Byzantines?
 Narrated Anas bin Malik:                     When the Prophet intended to write to the Byzantines, the people said, "They do not read a letter unless it is sealed (stamped)." Therefore the Prophet took a silver ring----as if I am looking at its glitter now----and its engraving was: 'Muhammad, Apostle of Allah'.