Answer
Wa`alaykum As-Salaamu Warahmatullahi Wabarakatuh.
In The Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
1- If you are obliged to work in this field, then there is nothing wrong, and you are excused for doing so.
2- You must repent to Allah, and ask Him to forgive you while striving hard to find another lawful way of earning a living.
Responding to the question, Sheikh `Abdus-Sattar Fathallah As-Sa`eed, Professor of Qur’an Exegesis and Qur’anic Sciences at Al-Azhar University, states:
We would like to clarify two important points. First, the economy is usually associated with riba (interest). If you are obliged to work in this field, then there is nothing wrong, and you are excused for doing so.
You must, however, repent to Allah, and ask Him to forgive you while striving hard to find another lawful way of earning a living.
Second, if you are directly involved in dealing with riba, and it is your career and means of earning a living, then you are not allowed to adopt this kind of work.
Finally, working in interest-based banks is not the normal choice of career for a Muslim. You are allowed to work there only if you find it extremely difficult to find a lawful way of earning a living.
Try to keep in mind that you should leave this job the moment you find a more suitable one. If you are driven by the sincere intention to find a lawful way to earn a living, Allah Almighty will make it easy for you.
Allah Almighty knows best.