"Blessed is the man to whom the Lord will not impute sin" (Romans 4:8).
The doctrine of imputation is a blessed truth to all who can claim it, even though the word itself is not much used today, even in theological circles. David's great psalm of thankful relief, after the Lord had forgiven him his gross sin in the matter of Bathsheba and Uriah, is the classic Biblical example.
David began this psalm with the words, "Blessed is he whose transgression is forgiven, whose sin is covered. Blessed is the man unto whom the LORD imputeth not iniquity, and in whose spirit there is no guile" (Psalm 32:1-2). David had prayed: "Create in me a clean heart, . . . and renew a right spirit within me" (Psalm 51:10), and God had answered.
Imputation is closely related to the doctrine of substitution, wherein an innocent person voluntarily takes the punishment assigned to the guilty, thereby setting the guilty one free. The sin is actually "imputed" to the innocent substitute while the guilty person receives by imputation the righteousness of the substitute.
Thus, as Paul preached, he noted that "God was in Christ, reconciling the world unto Himself, not imputing their trespasses unto them" (II Corinthians 5:19). That is, God made Christ "to be sin for us, . . . that we might be made the righteousness of God in Him" (II Corinthians 5:21).
Our text above stresses how great a blessing it is to a sinner when, because of the substitutionary sacrifice of Christ, his sin is no longer imputed to him. Perhaps even a greater blessing is realized when that sinner realizes not only that his sin is gone, but that he is a man unto whom "God imputeth righteousness without works" (Romans 4:6). We have amazingly been credited with the righteousness of Christ Himself, and this indeed makes us "blessed!" HMM