Therefore no one will be justified in His sight by works of the law. For the law merely brings awareness of sin.
20. Therefore by the works of the law, etc. It is a matter of doubt, even among the learned, what the works of the law mean. Some extend them to the observance of the whole law, while others confine them to the ceremonies alone.
From all this Paul infers that it is in vain to look for justification by the works of the law, and that it is to be had only by faith, which is the point he has been all along proving, from Rom 1:17, and which he lays down (Rom 3:28) as the summary of his discourse, with a quod erat demonstrandum - which was to be demonstrated.
Commenting on Romans 3:19-31
Being justified freely by his grace,.... The matter of justification is before expressed, and the persons that share in this blessing are described; here the several causes of it are mentioned. The moving cause of it is the free grace of God; for by "the grace of God" here, is not meant the Gospel, or what some men call the terms of the Gospel, and...