What should one do who finds a small piece of gold under a building inhabited by people of different nationalities? And should he sell it and donate its price to the poor?

If someone finds money of value, they must publicize it for a full year. If its owner does not come forward after this period, they should donate it as charity or benefit from it. If the owner comes later, they should hand it over to him or pay its value. If the owner is not pleased with the charitable donation, then the reward (for the donation) is for the finder.