To impute is to charge a thing upon a person whether guilty or not, as the circumstances hereafter are proved, or not. Thus Shimei intreated David, that he would not “impute iniquity to him” for some former transaction. (2 Samuel 19:19)
And the apostle Paul (Romans 4:8) declares them blessed to whom the Lord “will not impute sin.” This is the general sense of imputation.
But in the case of the imputed righteousness of the Lord Jesus Christ to his people, and their sins imputed to him; the sense of imputation goes farther, and ascribes to Christ, and to the sinner, that which each hath not, but by the very act of imputing it to them. Hence the apostle Paul explains it in the clearest manner in two Scriptures: the first, in 2 Corinthians 5:21, where speaking of this imputation of our sins to Christ, and his righteousness to us, he refers it into the sovereignty and good pleasure of God the Father.
For speaking of Christ, it is used, “God hath made him to be sin for us who knew no sin; that we might be made the righteousness of God in him.” Here the doctrine of imputation is most plainly and fully stated.
Christ is the imputed sinner, or rather sin itself in the total abstract, and in the very moment when he knew no sin.
And the sinner is said to be righteous; yea, the righteousness of God in Christ; when in the same time he hath not a single portion of righteousness in himself, or in any of his doings. This is, therefore, to impute Christ’s righteousness to his people, and their sins to him. The other Scripture that explains the doctrine is but in part, namely, respecting the imputation of sin.
“Christ hath redeemed us from the curse of the law, being made a curse for us.” (Galatians 3:13)
Here Christ stands with all the curse of a broken law charged upon him, as the sinner’s Surety; yea, as the curse itself. And consequently, as in the doing of this, he takes it from his people; they are redeemed from it. The original debtor, and the Surety, who pays for that debtor, cannot both have the debt at the same time charged, upon them. This, therefore, is the blessed doctrine of imputation. Our sins are imputed to Christ. His righteousness is imputed to us. And this by the authority and appointment of JEHOVAH; for without this authority and appointment of JEHOVAH, the transfer could not have taken place.
Robert Hawker (1753 – 1827)