A man found a purse containing one hundred Diners.
So he went to the Prophet (sallallähu alaihi wasallam) (and informed him about it), he said, “Make public announcement about it for one year”

He did so, but nobody turned up to claim it, so he again went to the Prophet (sallallähu alaihi wasallam) who said, “Make public announcement for another year.”

He did, but none turned up to claim it. He went to him for the third time and the Prophet (sallallähu alaihi wasallam) said, “Keep the container and the string which is used for its tying and count the money it contains and if its owner comes, give it to him; otherwise, utilize it.”

[Bukhari Book:42 No:608]