What is the ruling on money taken by a son from working in his father's shop, which sells prohibited items such as cigarettes, given that the son is aware of this and his mother has informed him that his father has permitted him to take whatever money he wishes?

If the father grants his son permission to take from his money, then it is permissible. Taking from a father's money that is mixed with lawful and unlawful earnings is permissible if the predominant part of his money is lawful. However, if all of the father's money is unlawful, then it is permissible for the son to take from it only to the extent of his need.