Is it permissible to remain with an Islamic bank that deals in usury under the guise of a "gift," or to switch to a usurious bank that has an "Islamic" division based on Mudarabah (profit-sharing) and deposits, and does not give interest?

Allah has forbidden usury and declared its perpetrator to be at war with Allah and cursed, as stated in His Almighty saying: "O you who have believed, fear Allah and give up what remains [due to you] of interest, if you should be believers. And if you do not, then be informed of a war [against you] from Allah and His Messenger." And the Prophet, peace and blessings be upon him, said: "Allah has cursed the one who consumes Riba (usury), the one who feeds it, and its two witnesses." Islamic banks were established to be an alternative to usurious banks and are not considered Islamic unless they adhere to the regulations of Sharia (definition). Therefore, any bank that guarantees capital or commits to a fixed profit is a usurious bank, even if it is called Islamic. As for the Islamic transaction branches in usurious banks, there is no harm in dealing with them if they abide by the rulings of Sharia and if all their investment channels are separate from the usurious bank.