What is the ruling on dealing with old shares in usurious banks, knowing that their owner was ignorant of the Shariah ruling at the time of their deposit?

It is impermissible to contribute to usurious banks, based on Allah’s Almighty saying: ﴿But 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 not wrong, nor are you wronged.﴾ If one gains profits from usurious transactions, he must dispose of them by spending them on charitable causes, such as giving to the poor and needy, and building hospitals. Your father must spend the returns from his shares on charitable causes, and he must reclaim the equivalent of what he contributed at the time of establishment, instead of reclaiming the shares themselves.