Introduction to Romans

The scope or design of the apostle in writing to the Romans appears to have been, to answer the unbelieving, and to teach the believing Jew; to confirm the Christian and to convert the idolatrous Gentile; and to show the Gentile convert as equal with the Jewish, in respect of his religious condition, and his rank in the Divine favour. These several designs are brought into on view, by opposing or arguing with the infidel or unbelieving Jew, in favour of the Christian or believing Gentile. The way of a sinner's acceptance with God, or justification in his sight, merely by grace, through faith in the righteousness of Christ, without distinction of nations, is plainly stated. This doctrine is cleared from the objections raised by Judaizing Christians, who were for making terms of acceptance with God by a mixture of the law and the gospel, and for shutting out the Gentiles from any share in the blessings of salvation brought in by the Messiah. In the conclusion, holiness is further enforced by practical exhortations.

-- taken from Matthew Henry's Concise Commentary