What is the ruling on money acquired from a bank deposit with a fixed monthly interest rate, and why do fatwas (religious edicts) differ between permissibility and prohibition regarding this matter?

If the bank specifies the amount of interest as a lump sum, then it is usury (riba), which is religiously forbidden, based on the Almighty's saying: ﴿O you who have believed, fear Allah and give up what remains [due to you] of riba if you should be believers. And if you do not, then be informed of a war [against you] from Allah and His Messenger. But if you repent, you may have your principal – [thus] you do no wrong, nor are you wronged.﴾ [Al-Baqarah: 278-279]. And the Prophet (peace be upon him) said: “Allah curses the one who consumes riba, the one who feeds it, and its two witnesses.” He also said: “They are equal [in sin].” Money resulting from usury is not permissible to possess; rather, it must be spent on general Muslim welfare, such as roads and hospitals, or on the poor and needy.

As for someone who dealt with riba out of ignorance of its prohibition or by imitating a fatwa that permits it, he may keep what he acquired before knowing of its prohibition, and he must cease it in the future. Some scholars cited the Almighty's saying: ﴿So whoever receives an admonition from his Lord and desists may have what is past, and his affair rests with Allah.﴾ However, if he was aware of its prohibition, then he must dispose of the riba by giving it in charity or to charitable projects.