All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah.
Islam has forbidden every act that leads to what is forbidden. Allah the Exalted says {what means}: “And do not cooperate in sin and aggression” [al-Māʾidah/2]. It is narrated on the authority of Jābir (may Allah be pleased with him) that he said: “The Messenger of Allah (peace and blessings be upon him) cursed the one who consumes ribā, the one who gives it to others, its scribe, and its two witnesses, and said: They are all alike.” Narrated by Imam Muslim. Imam al-Munāwī (may Allah have mercy on him) said: “He made them equal in the curse, that is, the one who consumes ribā, the one who gives it, its scribe, and its two witnesses, because the contract is not completed except through all of them together.” [Fayḍ al-Qadīr, Vol.1/p.54]
Forbidden assistance is therefore that which is direct or which is a cause leading to the forbidden. Every act that assists in the forbidden and serves as a means to it is forbidden like it, for means take the ruling of the objectives. This covers completion, execution, and promotion.
The ruling on working in programming systems for banks and companies in general varies according to the type of software designed. If the programs the employee will design are used in all kinds of banks, whether Islamic banks or interest-based (ribawī) banks, then the ruling on working on such a system returns to the principle on which Sharīʿah rulings are built, namely the original absence of liability, which indicates permissibility until evidence of prohibition arrives. If it is then sold to interest-based banks, the sin falls on the one who benefits from it in an unlawful way.
If, however, the program is designed only for interest-based banks and will be used in matters that assist their forbidden transactions, then working on designing it is forbidden, and we advise declining to design it.
As for an employee who works in a field that assists in the forbidden, if leaving his job would result in ruin for himself or loss for those he supports, this is tolerated out of necessity. He continues in his work until he finds another job, while remaining obliged to seek other work even with lesser benefits, based on the legal maxims: “Necessities permit the prohibited” and “Necessity is measured by its extent.”
This, then, is the general breakdown stated above, and the employee is best able to describe the nature of his own work. We remind of the saying of Allah the Mighty and Majestic: “And whoever fears Allah, He will make for him a way out, and will provide for him from where he does not expect. And whoever relies upon Allah, then He is sufficient for him.” [al-Ṭalāq/2-3], and that whoever leaves something for the sake of Allah, Allah will replace it with something better. And Allah Almighty knows best.
