Therefore; i.e. Seeing the Gentiles, by the law of nature, and the Jews, by the written law, are thus subject to the judgment of God; and seeing no one is able to fulfil the law, and satisfy for the breach of it; therefore, &c. By the deeds of the law; he means the moral law, and not the ceremonial law only or chiefly; even that law that forbids theft and adultery, as Romans 2:21,22, and concupiscence, as Romans 7:1-25; and by which, as this text says, is the knowledge of sin; to which Gentiles as well as Jews are obliged, and by which therefore they are condemned. No flesh; a common synecdoche: see Genesis 6:3,12, and elsewhere. The same with no man living, in the psalmist; especially being depraved with original corruption, which is called flesh in Scripture. Be justified in his sight; or be discharged in the court of heaven: the phrase is taken from Psalms 143:2, see annotations there. For by the law is the knowledge of sin: lest any should think that the law hereupon is useless, he goes on to show its use, but a quite contrary one to what they intended. It convinceth us of our guilt, and therefore is far from being our righteousness, Romans 7:7 1 Corinthians 15:56.
Related Commentaries of Romans 3:20
Romans 3:20
20 Therefore by the deeds of the law there shall no flesh be justified in his sight: for by the law is the knowledge of sin.