John Wesley on Romans 3:20

No flesh shall be justified - None shall be forgiven and accepted of God. By the works of the law - On this ground, that he hath kept the law. St. Paul means chiefly the moral part of it, Rom 3:9,19 Rom 2:21,26; &c. which alone is not abolished, Rom 3:31. And it is not without reason, that he so often mentions the works of the law, whether ceremonial or moral; for it was on these only the Jews relied, being wholly ignorant of those that spring from faith. For by the law is only the knowledge of sin - But no deliverance either from the guilt or power of it.