20. Therefore by the deeds of--obedience to
      the law there shall no flesh be justified--that is, be held and treated as righteous; as is plain from the whole scope and strain of the argument.
      in his sight--at His bar (Ps 143:2).
      for by the law is the knowledge of sin--(See on Ro 4:15; Ro 7:7; and 1Jo 3:4).

      Note, How broad and deep does the apostle in this section lay the foundations of his great doctrine of Justification by free grace--in the disorder of man's whole nature, the consequent universality of human guilt, the condemnation, by reason of the breach of divine law, of the whole world, and the impossibility of justification before God by obedience to that violated law! Only when these humiliating conclusions are accepted and felt, are we in a condition to appreciate and embrace the grace of the Gospel, next to be opened up.

JFB.