It was narrated that Ibn 'Umar said:"The Prophet [SAW] used to wear a ring of gold, then he discarded it, and put on a ring of silver on which was engraved (the words): 'Muhammad Rasul Allah.' He said: 'No one else should engrave his ring with an inscription like this ring of mine.' Then he put the stone toward the palm of his hand

English translation · Sunan an-Nasa'i