Working in a riba-based (interest-based) bank

You will find the answer in the hadeeth of Jaabir, may Allaah be pleased
with him, who said: “The Messenger of Allaah cursed the one who
consumes riba (interest or usury), the one who gives it, the one who writes
it down and the one who witnesses it. He said: ‘All of them are equal in
sin.'” (Reported by Muslim, may Allaah have mercy on him, in his Saheeh, no. 1598)

Commenting on this hadeeth, al-Nawawi, may Allaah have mercy on him,
said: This is clearly a prohibition of the writing down or witnessing of a
contract between the two parties involved in a riba-based deal. It also
includes a prohibition of helping others to commit wrong acts. And Allaah
knows best.

It is inevitable that the employee in a riba-based bank will play a part in riba
dealings one way or another, even if he is just a security guard. Maybe
Allaah will help you, my brother, if you are patient, to find halaal
employment. (Interpretation of the meaning) ” And whosoever fears
Allaah and keeps his duty to Him, He will make a way for him to get out
(from every difficulty).” [al-Talaaq 65:2]