What is the ruling on working for an institution whose resources include some bank interest, while receiving a fixed monthly salary and being unable to change this source of income?

If a person's work in an institution is Islamically permissible, and they receive a fixed salary for it, then their work is lawful and they bear no sin. This is because the company's funds are mixed, and their work is not directly or indirectly related to usury. It is advisable not to despair of counseling the institution to purify its resources.