Is money found inside an old shoe that was purchased lawful (halal) or unlawful (haram), and what should be done with it if it is unlawful?

The money either belongs to the seller, in which case it must be returned to him. If it is highly probable that it belongs to the shoe owners, then it must be made known and returned to them if possible. Otherwise, it should be spent on the welfare of the Muslims, similar to money whose owner cannot be reached, or it should be given as charity on behalf of its owner. Some scholars are of the opinion that the finder can own it without making it known.