Is it permissible to use unlawfully acquired money, of which some remains after repentance, to buy something for one's father, or must it be given as charity to the poor?

You must avoid money acquired through unlawful means, as it is not permissible for you to possess it. The ruling on such money varies:

- If it involves the right of another, such as stolen money: The right must be returned to its owner or their heirs. If that is not possible, then it should be given as charity on their behalf.

- If it does not involve the right of another (such as money gained from trading in unlawful things): You must dispose of it by spending it on the poor and needy, or on public welfare and charitable causes. The questioner is not permitted to spend from it on themselves or their parents, unless they are poor and have no other means, in which case it is permissible for them to benefit from it to the extent of their need.