27 Where is boasting then? It is excluded. By what law? of works? Nay: but by the law of faith. (Romans 3:27 KJV)
William Burkitt’s Commentary
Apostle Paul having laid down in the foregoing verses the nature of justification exactly in the several and respective causes of it, declares in this verse what is the consequence of this doctrine, namely, the excluding of all self-confidence and boasting in ourselves or in any works done by ourselves: Where is boasting then?
Learn hence, That man is naturally a very proud creature, prone to boast of, and glory in, any excellency, either real or supposed, belonging to himself.
Learn, 2. That God has taken care to give a check to this insolent pride of man, and to cut off all occasion of boasting from him, That no flesh should glory in his sight 1Co 1:29. Whilst God intended man glory, he took a course to cut off all glorying from man.
Learn, 3. That the course which the wisdom of God has taken to hide pride from man’s eyes, and to cut off all occasion of boasting from him, is by denying him justification by his own works; and ordaining that the meritorious cause of justification should not lie in himself, but in another.
Grace must have all the glory; not the law of works, but the law of faith justifies and saves all believers.