Is it permissible for a Muslim to supervise the building of a house, or manage a trade, or live in, or eat from money acquired by his Muslim brother through a prohibited usurious loan?

Taking a loan with stipulated interest is forbidden usury, for which Allah has declared war on its perpetrator. The Prophet, peace and blessings be upon him, cursed the one who consumes usury, the one who feeds it, its scribe, and its two witnesses. This brother must be advised and his action denounced. If cooperating with him pushes him to take a usurious loan, then it is impermissible, as Allah Almighty says: "And do not cooperate in sin and aggression." If he will take a loan in all circumstances, he should be ostracized if ostracism will deter him. However, eating from his shop is permissible.