Lange writes, An Epistle, sent to Rome by the ambassador of a Lord and King, who declared himself appointed to call all the peoples of the Roman Empire to obedience or allegiance, must have been planned in full consciousness of the antithesis, as well as of the analogy, between the earthly Roman Empire and the Kingdom of Christ. Therefore the Apostle expresses the analogy when he characterizes himself as an ambassador who appeals to the nations to be obedient to his Lord. But the antithesis lies in his denoting this obedience as an obedience to the faith. He says, The receivers by faith of the message are to obey it. For with the gospel go forth commands.
Faith is to show itself by obedience.
This view understands the faith to refer to the Gospel message . Grammatically this view is arrived at either by seeing the faith as the object of obedience or by seeing faith as appositional to obedience, that is, the obedience which is faith . Thus in this view the obedience in question is obedience to the Gospel message. Paul is aware that he is to bring the Gentiles thereto. Faith is an obedient response to the summons of the Gospel.