What is the ruling on the contract if I bear the costs of non-operational maintenance, and what should be done, given that the lease contract stipulates that the bank bears these costs, but it was later found that the maintenance is at the expense of the lessee?

The contract concluded with the bank is what is relied upon, and the bank must adhere to it and bear the costs of non-operational maintenance. It is not permissible for the bank to charge the lessee for the costs of this maintenance, because non-operational maintenance expenses are the responsibility of the lessor throughout the lease period.

The lessor’s condition that the lessee guarantee or maintain the leased property invalidates the contract, due to the resulting ambiguity in the amount of the rent, which is a gharar (excessive uncertainty) that nullifies the contract by agreement of the madhhabs (schools of thought).

The lessee has the right to refuse any conditions not included in the contract between him and the bank, but if he voluntarily performs the maintenance, there is no harm in it and it does not affect the contract.