Is it permissible to take a sum of money resulting from usurious interest with the pure intention of purchasing a key to a home?

It is impermissible to transfer client files to a usurious bank, and the increase made by the bank on the debt is prohibited interest (riba). Whoever deals with usury is declared to be at war with Allah and His Messenger. Selling a deferred payment for a deferred payment (debt for debt) is forbidden.

This transaction must be annulled and any payments retrieved if possible. However, if you are compelled to complete the deal, there is no sin upon you, for the Prophet, peace and blessings be upon him, said: "Indeed, Allah has pardoned for my Ummah their mistakes, their forgetfulness, and what they are compelled to do."

As for money resulting from usurious interest, it is ill-gotten wealth that must be spent on general Muslim welfare, such as for the poor and the needy. You may take it if you are poor and in need; otherwise, you may not.

Your father must withdraw his money from usurious institutions.