What is the ruling on money borrowed from the bank with usury to buy a house, when the purchase was not completed with it, and how should one dispose of it, and what is the legal ruling on the father who borrowed it?

Your father erred by taking out a usurious loan to buy the house, as usury is forbidden in Islam and severe warnings against it have been mentioned in the Qur’an and Sunnah.

He must repent sincerely to Allah. He should go to the bank to pay off the remaining amount. If they reduce the interest, then good; if not, we hope that Allah will forgive him as long as he has truly repented.