The World Federation One Stop Fiqh

Ruling 1834

If a person pays khums on lawful property that has become mixed with unlawful property, or if he gives some property as ṣadaqah on behalf of the owner who is unknown to him and later the owner is found, then in the event that the owner does not agree [to the action taken], based on obligatory precaution, the person must reimburse him his share.