What is the ruling on taking out an interest-bearing loan from a bank to purchase bakery equipment, given that the bank adds 15% as interest on the total amount, with the father's house as collateral?

If the bank buys the equipment and takes possession of it, then sells it to you at an agreed-upon profit, and you pay the price in installments, then this is permissible. Murabaha to the one who promises to buy is permissible, provided that the commodity enters the ownership of the one who is commanded to buy, and the responsibility for its damage transfers to him before delivery, along with the fulfillment of the conditions of sale and the absence of its impediments. As for the promise, it is binding upon the promisor religiously unless there is an excuse, and legally if it is contingent upon a cause and the promisee incurs a cost. However, a mutual promise (Muwada’ah Mushtaraka) is permissible provided there is an option for one or both parties; otherwise, it is not permissible because it resembles the sale itself, and the seller must own the sold item. But if the bank pays the price of the equipment on your behalf and charges interest, this is a forbidden usurious loan.