What is the ruling on dealing with a bank that pays me an amount equivalent to the cost of living index to preserve the purchasing power of my money?

Keeping money amidst high living costs causes it to lose its purchasing power, which prompts some to deposit it in usurious banks and take interest. This is forbidden in Islamic law because it is usury (riba). Allah has warned those who consume it of war, and the Prophet, peace and blessings be upon him, cursed the one who consumes it, the one who feeds it, its scribe, and its two witnesses. Therefore, depositing money in banks with interest is a forbidden usurious loan.

It is not permissible to stipulate interest on loans, even if the value of the money decreases. Investment certificates with a fixed return are impermissible. The decrease in the purchasing power of money does not justify making usurious interest permissible. The nominal value of the certificates is permissible, but the interest is usury that must be disposed of by spending it on charitable causes. It is not permissible for a Muslim to benefit from it.

If there is fear of money being stolen, it is permissible to place it in a current account in usurious banks without taking interest. If interest accrues from it, it must be disposed of by spending it on the poor, the needy, and for public welfare, and it is not permissible to benefit from any part of it.