Sahih Bukhari: Hadith 5665

The ring of the Prophet (ﷺ) was in his hand, and after him, in Abu Bakr's hand, and then in `Umar's hand after Abu Bakr. When `Uthman was the Caliph, once he was sitting at the well of Aris. He removed the ring from his hand and while he was trifling with it, dropped into the well. We kept on going to the well with `Uthman for three days looking for the ring, and finally the well was drained, but the ring was not found.