God does not require more than we are able to give - but he does want all we can give. So natural ability is assumed by the command of God. God does not require what you don't have. God only require that which we are able to give. Notice that willing is all that is required.
Love is willing the highest good.
Love is the fulfillment of the law. Therefore willing is all the moral law requires. Such passages clearly teach natural ability. Many more proofs could be given, but these will suffice. Objections Answered Someone might object that we are saved by faith not by works, therefore we are no longer obligated to obey the law.