Is it permissible to dispose of the father’s money, held in an interest-based bank—by virtue of a power of attorney from him—to start a project without his knowledge, after he refused to transfer or withdraw it, and due to his failing eyesight and old age?

Usury (riba) is forbidden and is one of the gravest prohibitions. Allah has threatened those who engage in it with the direst consequences in this world and the hereafter. Allah Almighty says: "Those who consume interest will not stand [on the Day of Resurrection] except as one stands who is being beaten by Satan into insanity." And Allah Almighty says: "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." The Prophet, peace and blessings be upon him, said: "Allah has cursed the one who consumes riba, the one who feeds it, its scribe, and its two witnesses."

Changing an evil is a religious obligation for whoever is able, according to the saying of the Prophet, peace and blessings be upon him: "Whoever among you sees an evil, let him change it with his hand; if he cannot, then with his tongue; if he cannot, then with his heart—and that is the weakest of faith." Therefore, if your father has given you absolute power of attorney over his money, it is your duty to withdraw it from interest-based banks by any possible means.