Working in A Usurious Bank Is Absolutely Prohibited
24-3-2020 | IslamWeb
Question:
How can it be that working in a non Islamic bank is prohibited even when one’s job is in no way at all whatsoever involved in riba or help in committing riba? Like giving or taking cash, currency exchange, etc. Only the loans and the interest gained on savings is haraam.
Answer:
All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad 
is His slave and Messenger.
The view that it is absolutely prohibited to work in Riba-based (usurious) banks, even in a job that does not entail direct involvement in Riba (interest/usury) transactions, is based on the fact that the work of an employee in such Riba-based institutions is never devoid of helping others commit prohibitions. Jobs, in any given institution, complement each other and it is forbidden for a Muslim to help others commit sin and evil; Allah, The Exalted, Says (what means): {And cooperate in righteousness and piety, but do not cooperate in sin and aggression.} [Quran 5:2]
It is well known that the sin of dealing with Riba is not confined to the one who consumes it and the one who pays it to others to consume, rather, it extends to everyone who contributes to conducting the Riba-based transactions. The Prophet said: “Allah has cursed the one who consumes Riba, the one who pays it, the one who records it, and the two witnesses to it.” He added: “They are equal (meaning in sin).” [Muslim]
An-Nawawi 
said: “This is an explicit prohibition of recording or witnessing a Riba-based sale contract between a buyer and seller. This also includes the prohibition of helping others commit wrongful acts.” [End of quote]
Additionally, working in Riba-based banks, whether it is in the currency exchange department, giving or taking cash, or any other task that is not connected to Riba-based contracts; this often entails helping others conduct Riba-based contracts, approving them, keeping silent about their sinfulness, and refraining from forbidding them.
The Fatwa of the Permanent Committee 15/41 reads: “It is impermissible for a Muslim to work in a Riba-based bank even if his job does not involve dealing with Riba directly, because he is providing the employees who are directly involved in Riba-based transactions with what they need to carry out their Riba-related work.” [End of quote]
Allah Knows best.