"As has already been said, there can be no justification in a legal or forensic sense, but upon the ground of universal, perfect, and uninterrupted obedience to law. This is of course denied by those who hold that gospel justification, or the justification of penitent sinners, is of the nature of a forensic or judicial justification. They hold to the legal maxim, that what a man does by another he does by himself, and therefore the law regards Christ's obedience as ours, on the ground that he obeyed for us. To this I reply:
1. The legal maxim just repeated does not apply, except in cases where one acts in behalf of another by his own appointment, which was not the case with the obedience of Christ; — and;
2. The doctrine of an imputed righteous- ness, or that Christ's obedience to the law was accounted as our obedience, is founded on a most false and nonsensical assumption; to wit, that Christ owed no obedience to the law in his own person, and that therefore his obedience was altogether a work of supererogation, and might be made a substitute for our own obedience; that it might be set down to our credit, because he did not need to obey for himself.
I must here remark, that justification respects the moral law; and that it must be intended that Christ owed no obedience to the moral law, and therefore his obedience to this law, being wholly a work of supererogation, is set down to our account as the ground of our justification upon condition of faith in him. But surely this is an obvious mistake. We have seen that the spirit of the moral law requires good will to God and the universe. Was Christ under no obligation to do this? Nay, was he not rather under infinite obligation to be perfectly benevolent? Was it possible for him to be more benevolent than the law requires God and all beings to be? Did he not owe entire consecration of heart and life to the highest: good of universal being? If not, then benevolence in him were no virtue, for it would not be a compliance with moral obligation. It was naturally impossible for him, and is naturally impossible for any being, to perform a work of supererogation; that is, to be more benevolent than the moral law requires him to be. This is and must be as true of God as it is of any other being. Would not Christ have sinned had he not been perfectly benevolent? If he would, it follows that he owed obedience to the law, as really as any other being. Indeed, a being that owed no obedience to the moral law must be wholly incapable of virtue, for what is virtue but obedience to the moral law?
But if Christ owed personal obedience to the moral law, then his obedience could no more than justify himself. It can never be imputed to us. He was bound for himself to love God with all his heart, and soul, and mind, and strength, and his neighbor as himself. He did no more than this. He could do no more. It was naturally impossible, then, for him to obey in our behalf."
From Finney's Systematic Theology, Charles Finney, 1846; abridged, 1976,