Is it Islamically permissible to participate in purchasing a car by installments, and then lease it to a car showroom for a monthly fee, knowing that the showroom will then lease it to people, and that insuring the car is a condition for leasing it to the showroom? And are we held accountable if the lessee uses the car for sinful purposes? And is this substantial profit permissible?

It is permissible to rent out a car to a rental office for a specified amount, and for the office to rent it out after taking possession of it for the same, more, or less than the rent. The rented car is a trust (amanah), and the renter is not liable for it except in cases of negligence or transgression. Therefore, it is not permissible to stipulate that the office guarantees the car absolutely; the guarantee is limited to cases of transgression and negligence. As for commercial insurance, it is forbidden, while cooperative insurance is permissible. The car owner is not required to know the renter's situation or whether they will use it for sinful purposes; people are to be presumed good unless proven otherwise. If the rental agreement is valid, there is no harm in the return from it, even if it is substantial or did not require significant effort.