Is it permissible to take money of suspicious origin—its source being work in a hotel that serves alcoholic beverages—to start a private project out of extreme necessity, and then to donate the same amount after investing it?

It is permissible for you to accept a gift from your brother and benefit from it if you are in need of it for your daily sustenance or to establish a project, whether his wealth is mixed with lawful and unlawful sources, or if all his wealth is unlawful. A needy person is permitted to take unlawful money to the extent of his need, and it becomes lawful for him. Imam Al-Nawawi said: "If he gives it - the unlawful money - to the poor, it is not unlawful for the poor person; rather, it is lawful and good. He may give charity from it to himself and his family if he is poor... And he himself may take what suffices his need, because he is also poor." You are not required to give charity in exchange for this money if you become wealthy later. It is, however, recommended that you advise your brother to abandon unlawful work and seek a job free from doubt.