Abu Dawud Book 29, Hadith Number 4206.

Chapter : Fashioning a seal in the form of a ring.

Narated By Ibn ‘Umar : The Apostle of Allah (PBUH) took a signet-ring of gold, and put the stone next the palm of his hand. He engraved on it “Muhammad, the Apostle of Allah.” The people then took signet-rings of gold. When he saw that they had taken them (like his ring), he threw it away and said: I shall never wear it. He then fashioned a silver ring and engraved on it “Muhammad, the Apostle of Allah.” Then Abu Bakr wore it after him, then ‘Umar wore it after Abu Bakr, and then ‘Uthman wore it after ‘Umar till it fell down in a well called Aris.

Abu Dawud said: The people did not disagree on ‘Uthman till the signet-ring fell down from his hand.