Is it permissible to purchase a house through a bank transaction in which the buyer and seller sign a pledge of sale, the house is designated to the bank, then the bank purchases the house, and the buyer begins paying a rental sum to the bank for a specified period, after which the house becomes the property of the payer of the sum?

The pledge made by the client to the bank to rent a house after the bank purchases it is permissible if it is a binding promise that necessitates either renting or paying compensation for damages in case of reneging, and it is binding upon the client. However, if the pledge is a lease contract, it is invalid because the bank is contracting for something it does not yet own.