Commentaries:
Robertson's Word Pictures (NT)
Because (dioti, again, dia, oti).
By the works of the law (ec ergwn nomou). "Out of works of law." Mosaic law and any law as the source of being set right with God. Paul quotes Psalms 43:2 as he did in Galatians 2:16 to prove his point.
The knowledge of sin (epignwsiv amartiav). The effect of law universally is rebellion to it (I Corinthians 15:56). Paul has shown this carefully in Galatians 3:19-22. Cf. Hebrews 10:3. He has now proven the guilt of both Gentile and Jew.
Other Robertson's Word Pictures (NT) entries containing Romans 3:20:
Ephesians 2:3
Titus 3:5
2 Peter 3:16
DISCLAIMER: Church of the Great God (CGG) provides these resources to aid the individual in studying the Bible. However, it is up to the individual to "prove all things, and hold fast to that which is good" (I Thessalonians 5:21). The content of these resources does not necessarily reflect the views of CGG. They are provided for information purposes only.