Is it permissible to borrow from a friend whose account is handled by an interest-based bank?

It is permissible to take a benevolent loan from someone who deposits their money in usurious banks, as long as the borrowed money itself is not illicit. The Prophet, peace be upon him, engaged in buying and selling with Jews and accepted their gifts, even though they dealt in usury.

It is narrated that Ibn Mas'ud said, "Its benefit is for you, and its sin is upon him," regarding someone invited by their neighbor who consumes usury. Al-Hasan was asked about eating the food of money changers and he replied, "Allah has elevated you above the Jews and Christians; they consume usury, yet He has made their food lawful for you."

Sheikh Ibn Uthaymeen mentioned that it is permissible for a person to deal with a usurer in buying, selling, and borrowing, as long as the transaction itself is sound, because the Prophet, peace be upon him, dealt with the Jews despite their consumption of ill-gotten gains.

One should advise their friend not to deposit their money in usurious banks unless absolutely necessary.