Is working in banks in the sales department to market and sell loans and credit cards unlawful (haram) or not? If it is unlawful, must one leave it immediately, or can one continue in it until another job opportunity becomes available? Does this work fall under the category of major sins regarding consuming usury (riba)? And is the one who consumes usury the bank owner, or is it him and those who work at the bank?

Everything that aids in usury (riba) is forbidden, based on the Almighty’s saying: "And do not cooperate in sin and aggression." If banks deal with usury, then their loans and cards are not Islamically regulated. One must immediately leave such work unless there is a necessity (such as someone who cannot meet their own needs or those of their dependents); in such a case, it is permissible to remain only for the duration of that necessity, while striving to find lawful employment. Continuing to work in a way that supports usury without great necessity is a major sin, because the curse includes the one who consumes usury, the one who feeds it, its scribe, and its two witnesses. And a curse is only for major sins.