Dealing with the one who involves in Riba
1-1-2004 | IslamWeb
Question:
Is it completely Haram to work in the banks? I investigated this a lot of times but somehow I find it difficult as I feel more or less all the salaries of different companies may be coming from the interest as they must have invested money so why is it said that it is Haram to work in banks even though the person is not taking interest he is getting paid for his service like he/she would have got to work for any other organization. I am really confused with this question and have a doubt in my heart. Please help me and make me understand y or y not all the possible reasons looking forward to your helpful reply.
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad 
is His slave and Messenger.
The inquiring sister didn't differentiate between dealing with usury and dealing with the one who involves in Riba (usury and/or interest). Dealing with usury is strictly prohibited including working in usurious banks. The money that is earned by unlawful sources is itself ill-gotten and one should get rid of such money. But dealing and working with a usurer in permissible transactions is allowed (legitimate); just as working for a lawful company or establishment which credits or invests in usurious banks. It is a wages for a legal work except if the whole capital of the company is ill-gotten, in which case the salary is consequently unlawful.
The evidence is as follows:
Firstly, money and dealing with money is permissible in principle. Its prohibition is not confirmed due to mere probability. But if lawful and ill-gotten money are mixed up, it is mere appropriate for the Muslim to give up dealing with these, out of piety.
Secondly, it is probable to deal with legal or illegal money. If it is not certain that something is unlawful, so its prohibition is not confirmed. It's obvious that whatever is in the person's hand is his.
Thirdly, when ill-gotten money is mixed with lawful money, it permeates in it. If you deal within it, you deal with a prohibited part, so it becomes a forbidden border-case issue for prevention of indulging in what is forbidden. Whatever you avoid for the sake of prevention is hateful, not forbidden.
Fourthly, the Prophet and his Companions 
were dealing with the Bedouin polytheists in Madeenah, though they were wrong doers and indulged in sins. The Bedouins had illicit wealth gathered by plunder, brigandry and usury. The Muslims’ money will be subdued to analogical deduction of non-Muslims’ money unanimously by scholars. What we have just mentioned only concerns those who deal with usurers in ordinary transactions or helpmates. But dealing or helping them with usurious transactions is strictly prohibited including renting buildings to them, crediting cash with them, guarding and cleaning up the usury establishment and printing and photo copying in that building. All these actions are clearly meant in the Quran. Allaah Says (what means): {And cooperate in righteousness and piety, but do not cooperate in sin and aggression. And fear Allaah; indeed, Allaah is severe in penalty.}[Quran 5:2]
It's beyond doubt that whoever offers any kind of help to usury transactions and usurers in writing and documentation, hoisting their belongings, or making food for them, or likewise are helpers in sin and transgression.
Allaah Knows best.