What is the ruling on the return on money deposited in the bank, and does the ruling differ between Islamic banks and others?

Mixing up financial returns from Islamic banks and usurious banks is a mistake. The contract with an Islamic bank is a Mudarabah (definition) (profit-sharing) agreement, where the customer gives money to the bank for investment, and the customer receives a percentage of the profit. This Mudarabah is permissible. As for usurious banks, the customer lends money to the bank in exchange for a fixed interest rate on the capital, which is clear riba (usury).

The occurrence of Sharia (definition) violations by Islamic banks does not equate to what usurious banks do. Islamic banks were established on the basis of finding a permissible alternative for banking operations, while usurious banks operate on usurious dealings. Allah has permitted trade and forbidden riba. Most of the errors of Islamic banks result from adopting weak opinions, and what is obligatory is not to adopt an opinion that contradicts the evidence.