What is the ruling on giving money to someone who will use it to commit a sin, whether the giver knows or does not know about it?

There is no harm in giving money to someone whose situation you are unaware of, and you do not predominantly believe they will use it for something unlawful. The sin is on them alone if they use it for such a purpose. However, for someone you know will use the money for something unlawful, it is forbidden to give them money, as it constitutes aiding in sin; as Allah Almighty says: "And do not cooperate in sin and aggression." Therefore, it is forbidden to give voluntary charity to a dissolute person who would use it to commit sin.