Is it permissible for a young man who found a large bag of money buried under a bridge to dispose of it or trade with it?

A found item (Luqatah) is inviolable property exposed to loss. The surrounding context defines it as picking up a lost item for safekeeping for others, not for ownership. Picking up an item is forbidden for someone who knows they are untrustworthy, disliked (Makruh) for someone who fears they might not fulfill their duty, and for the trustworthy, it is either recommended (Istihbab) or disliked (Karahah). Buried money does not cease to be the property of its owner, and it is not permissible to dispose of it. If it is highly probable that the money is stolen, it must be handed over to a legitimate judge or a just ruler.