Is it a sin for me to buy a car through a lease-to-own installment plan, at my father's request, knowing that this type of transaction is forbidden?

Installment sales are permissible if they adhere to Islamic legal principles. Similarly, lease-to-own agreements have various forms, some of which are permissible and some forbidden. Therefore, the nature of the transaction must be verified before engaging in it. If it is permissible, then there is no issue. If it is forbidden, then it is not permissible to engage in it, and there is no obedience to the parent in this matter, for the Prophet, peace and blessings be upon him, said: "There is no obedience to a creature in disobedience to Allah." This should be done with gentleness in apologizing and striving to find a permissible alternative.