What should a person do who took Zakat and charity money while not being eligible for it, and has now repented: should he return it to its owners or give it away as charity on their behalf? And which is better?

Funds taken without entitlement, whether zakat or sadaqa, must be returned to the entity from which they were taken, because they are the agents of their owners. If they were taken from individuals, they must be returned to them if possible; otherwise, they should be given to an organization to distribute them to those entitled to them. Sincere repentance for what has occurred is also required.