And that it is absolutely necessary thus it should be, is evident, both with respect to God and also with respect to man.
With respect to God. The righteousness is demanded by God; therefore he that comes to redeem must present before God a righteousness absolutely perfect; this can be done by none but God.
With respect to man. Man was to present this righteousness to God; therefore must the undertaker be man. Man for man, and God for God, God-man between God and man. This daysman can lay his hand upon us both, and bring God and man together in peace (Job 9:33).
Quest. But some may say, what need of the righteousness of one that is naturally God? Had Adam, who was but a mere man, stood in his innocency, and done his duty, he had saved himself and all his posterity.
Answ. Had Adam stood, he had so long secured himself from the wages of sin, and posterity so long as they were in him. But had Adam sinned, yea, although he had not defiled his nature with filth, he could never after that have redeemed himself from the curse of the law, because he was not equal with God; for the curse of the law is the curse of God; but no man can deliver himself from the curse of God, having first transgressed. This is evident, because angels, for sin, lie bound in chains, and can never deliver themselves. He, therefore, that redeemeth man from under the law must not only do all the good that the law requireth, but bear all the penalty that is due by the law for sin.
Should an angel assume human flesh, and in that flesh do the law, this righteousness would not redeem a sinner; it would be but the righteousness of an angel, and so, far short of such a righteousness as can secure a sinner from the wrath of God. But 'thou shalt love the Lord thy God with all thy soul, with all thy heart, with all thy mind, with all thy strength.' If there were no more required of us now to redeem ourselves, it would be utterly impossible for us to do it, because in the best there is sin, which will intermix itself with every duty of man. This being so, all the heart, all the soul, all the strength, and all the mind, to the exact requirement of the justice of the law, can never be found in a natural man.
Besides, for this work there is required a perfect memory, always to keep in mind the whole duty of man, the whole of every tittle of all the law, lest sin come in by forgetfulness; a perfect knowledge and judgment, lest sin come in by ignorance; an everlasting unweariedness in all, lest sin and continual temptation tire the soul, and cause it to fail before the whole be done.
For the accomplishing of this last, he must have—1. A perfect willingness, without the least thought to the contrary. 2. Such a hatred of sin as is not to be found but in the heart of God. 3. A full delight in every duty, and that in the midst of all temptations. 4. A continuing in all things to the well-pleasing of the justice of God.
I say, should the penalty of the law be taken off, should God forgive the penalty and punishment due to sins that are past, and only demand good works now, according to the tenor of the law, no man could be saved; there would not be found that heart, that soul, that mind, and that strength, anywhere in the world.
This, therefore, must cease for ever, unless the Son of God will put his shoulder to the work; but, blessed be God, he hath done it—'When the fulness of the time was come, God sent forth his Son, made of a woman, made under the law, to redeem them that were under the law.'