Sahih al-Bukhari — Lost Things Picked up by Someone (Luqatah) — Hadith No: 2437
Translation
Narrated Suwaid bin Ghafala:While I was in the company of Salman bin Rabi`a and Suhan, in one of the holy battles, I found a whip. One of them told me to drop it but I refused to do so and said that I would give it to its owner if I found him, otherwise I would utilize it. On our return we performed Hajj and on passing by Medina, I asked Ubai bin Ka`b about it. He said, "I found a bag containing a hundred Dinars in the lifetime of the Prophet (ﷺ) and took it to the Prophet (ﷺ) who said to me, 'Make public announcement about it for one year.' So, I announced it for one year and went to the Prophet (ﷺ) who said, 'Announce it publicly for another year.' So, I announced it for another year. I went to him again and he said, "Announce for another year." So I announced for still another year. I went to the Prophet (ﷺ) for the fourth time, and he said, 'Remember the amount of money, the description of its container and the string it is tied with, and if the owner comes, give it to him; otherwise, utilize it