Romans 15:17

I have therefore my glorying in Christ Jesus in things pertaining to God. For I will not dare to speak any things save those which Christ wrought through me, for the obedience of the Gentiles, by word and deed.

I have therefore, ... means, "I do have the right to tell of the things God has done through me." Such a right derived from Paul's desire to enlist the aid and encouragement of the brethren in Rome for his projected missionary journey to Spain. If they were to aid Paul, they were entitled to know of Paul's success; and, therefore, Paul had a right to speak of the success God had given him. Paul freely allowed that others had labored in the conversion of Gentiles, but he would speak only of the things God had accomplished through himself.

Obedience of the Gentiles ... in word and deed ... brings into view the true definition of Paul's doctrine of justification by faith. It certainly was not the "faith only" of Protestant theology, but the "obedience of faith" as affirmed at the beginning and the end of this epistle (Romans 15:1:5; Romans 16:26). If Paul had entertained any part of the theory of salvation by faith only, he could never have written anything like this verse. The Gentiles were obeying God! Indeed, does anything else really matter?

By word and deed ... is usually edited out of this, as having no reference to Gentile obedience, and applied to Paul's actions in preaching the gospel; but the proximity of the word to "Gentiles" and the obvious connection with their "obedience" leaves the overwhelming impression that they apply to the type of Gentile obedience which had been induced by Paul's preaching.