What is a usurious bank, and does working in an institution that pays your salary through a bank presumed to be usurious make the salary unlawful, and what should be done in this case?

Riba (usury/interest) is a specific increase for one of the contracting parties, devoid of any مقابل (counter-value) for it. It is divided into two types: 1. Riba al-Duyun (Interest on Debts): An increase in debt in exchange for an extension of the term. This is forbidden by the Qur’an. 2. Riba al-Buyu (Interest on Sales): This occurs in the sale of the six usurious commodities (gold, silver, wheat, dates, salt, barley) and what is analogous to them. It is divided into: Riba al-Fadl (Interest of Excess): An increase in one of the two عوضين (counter-values) over the other when selling a usurious commodity for another usurious commodity of the same type. Riba al-Nasi'ah (Interest of Delay): The delay in the قبض (taking possession) of one of the two عوضين (counter-values) in the sale of usurious commodities if they share the same علة (underlying reason/cause).

If the bank from which the salary is received is usurious, it is obligatory to transfer the salary to an Islamic bank. It is not permissible to keep the salary in a usurious bank except in cases of extreme necessity, provided that the salary is withdrawn immediately upon its deposit and not left in the current account.