John Wesley on Romans 3:19

Whatsoever the law - The Old Testament. Saith, it saith to them that are under the law - That is, to those who own its authority; to the Jews, and not the gentiles. St. Paul quoted no scripture against them, but pleaded with them only from the light of nature. Every mouth - Full of bitterness, Rom 3:14, and yet of boasting, Rom 3:27. May become guilty - May be fully convicted, and apparently liable to most just condemnation. These things were written of old, and were quoted by St. Paul, not to make men criminal, but to prove them so.