Sunan Ibn Majah Book 18, Hadith 6
He said: “Announce it for a year, then if someone describes it with its features, return it to him. If no one claims it, then remember the features of its leather bag and strap, and consume it (use it). Then if its owner comes along, give it to him.”
“I went out with Zaid bin Suhan and Salman bin Rabi'ah, and when we were at `Udhaib, I found a whip. They said to me: 'Throw it away,' but I refused. When we came to Al-Madinah I went to Ubayy bin Ka'b and told him about that. He said: 'You did the right thing. I found one hundred dinar that had been lost at the time of the Messenger of Allah (ﷺ), and I asked him about it. He said, “Announce it for a year.” So I Announced it, and I did not find anyone who recognized it. He said: “Remember the features of its bag and strap, and how many it contains, then announce it for a year. If someone comes who describes it with those features, (give it to him), otherwise it is like your own property.”
That he went out one day to Al-Baqi', which is the graveyard, to relieve himself. People used to go out to relieve themselves only every two or three days, and their faces was like that of a camel (because of hunger and rough food). Then he entered a ruin and while he was squatting to relieve himself, he saw a rat bringing a Dinar out of a hole, then it went in and brought out another, until it had brought out seventeen Dinars. Then it brought out a piece of red rag.Miqdad said: “I picked up the rag and found another Dinar inside it, thus completing eighteen Dinar. I took them out and brought them to the Messenger of Allah (ﷺ), and told him what had happened. I said, 'Take its Sadaqah (charity), O Messenger of Allah (ﷺ).' He said: 'Take them back, for no Sadaqah is due on them. May Allah (SWT) bless them for you.' Then he said: 'Perhaps you put your hand in the hole?' I said: 'No, by the One Who has honored you with the truth.”