Is it permissible to return money to a friend who was a partner in gambling after repenting, knowing that it was taken from him without his knowledge?

It is not permissible to create accounts for gamblers, due to the assistance it provides in sin, and the money resulting therefrom is unlawful (haram (definition)). If someone hires a person to perform an unlawful act and then repents, they should not give the wages to the worker but rather donate them as charity. However, if someone borrows or seizes unlawful money to gain from it, they must return it. Taking money without the owner's permission is usurpation (ghasb) and obliges its return, along with advising the owner to abandon unlawful acts. As for money taken by the owner before knowing it was unlawful, they may benefit from it. But if they took it after knowing it was unlawful, they must dispose of it by giving it to the poor or spending it on public welfare, unless they are in need, in which case they may take from it what suffices their need.