What is the ruling on variable interest rates and the returns on investment certificates in Islamic banks, such as Faysal Islamic Bank, given that my salary is transferred to a usurious bank and the Egyptian Dar Al-Ifta has permitted me to [deal with] interest and [investment] certificates?

The salary must be withdrawn from the usurious bank and not left there for the bank to profit from it. It is permissible to open an account and invest money in an Islamic bank and benefit from its profits if it invests money in permissible ways, and there is no harm in entering into a transaction that has been approved by the competent Fatwa authority.