Is the income earned from working in a non-Islamic bank that provides financing services for small and medium-sized enterprises through technical and financial studies, and sets an interest rate—knowing that the bank's capital is contributed by individuals and the state, and salaries are paid by the Ministry of Finance—lawful or unlawful? And what should someone who worked in it, ignorant of the ruling, do?

If the bank pays for the equipment on behalf of the buyer to be repaid in installments with an increase, this is a forbidden usurious loan (riba), and it is not permissible to continue working in it, due to the hadith: "Allah has cursed the one who consumes riba, the one who feeds it, its scribe, and its two witnesses," and he said, "they are all equal." It is not permissible to work in it, even if you are not among those who write or witness riba, because it involves aiding in sin. As for past salaries, what has passed is yours if you repent to Allah, as Allah the Almighty says: "So whoever receives an admonition from his Lord and desists, then what has passed is his, and his affair is entrusted to Allah."