Romans 4:8 - Albert Barnes' Notes on the Bible

Will not impute sin - On whom the Lord will not charge his sins; or who shall not be reckoned or regarded as guilty. This shows clearly what the apostle meant by imputing faith without works. It is to pardon sin, and to treat with favor; not to reckon or charge a man’s sin to him; but to treat him, though personally undeserving and ungodly Romans 4:5, as though the sin had not been committed. The word “impute” here is used in its natural and appropriate sense, as denoting to charge on man what properly belongs to him. See the note at Romans 4:3.