Will I be sinful if I sell a found gold item and donate its price, with the intention of giving its value to its owner if he is found and does not approve of my action, especially since I found it in a large city?

An important lost item (luqata) must be publicly announced for a year in public gatherings, two or three times each month. If its owner is identified, it should be handed over to them. Otherwise, it belongs to the finder after the year, except in the Two Holy Mosques (Mecca and Medina). In these two places, it is not permissible to claim ownership; rather, it must be announced perpetually or handed over to the responsible authorities. As for an insignificant lost item, it does not require announcement, and the finder may benefit from it or give it away as charity. An exception to this is a stray camel or animals that can defend themselves against small predators; these should not be picked up.