Q. 40. Why was it requisite that the mediator should be God and man in one person?
A. It was requisite that the mediator, who was to reconcile God and man, should himself be both God and man, and this in one person, that the proper works of each nature might be accepted of God for us, and relied on by us, as the works of the whole person.
Why could not God provide two Mediators, one divine and the other human, to accomplish the salvation of his people from sin? Because the relation between the works of each of the two natures required that these two natures be united in one person. A divine Mediator could not experience suffering except through a human nature; a human Mediator could not endure the required suffering, except as sustained by a divine nature. Therefore it was necessary, not only that the Mediator be God and that he be man, but that both natures be united in one person that his work might be a unity.
What work of Christ’s divine nature does Scripture speak of as part of the work accomplishing our salvation? Hebrews 9: 14. It was through the eternal Spirit that Christ offered himself a sacrifice to God for our sins. This may be translated “through his eternal Spirit” (see the ARV margin). In any case, the meaning is probably not “through the Holy Spirit,” but rather “through his own divine nature”; that is, it was through his divine nature that Christ offered hiniself as a sacrifice to God for the sins of his people; his divine nature gave value and efficacy to the sacrifice and sufferings of his human nature.
What work of Christ’s human nature does Scripture speak of as a part of the work of accomplishing our salvation? Scripture speaks of Christ’s obedience to the law, and of all his sufferings, and especially his death, all of which were works of his human nature, as essential parts of the work of accomplishing our salvation.