15:14-21 The apostle was persuaded that the Roman Christians were filled with a kind and affectionate spirit, as well as with knowledge. He had written to remind them of their duties and their dangers, because God had appointed him the minister of Christ to the Gentiles. Paul preached to them; but what made them sacrifices to God, was, their sanctification; not his work, but the work of the Holy Ghost: unholy things can never be pleasing to the holy God. The conversion of souls pertains unto God; therefore it is the matter of Paul's glorying, not the things of the flesh. But though a great preacher, he could not make one soul obedient, further than the Spirit of God accompanied his labours. He principally sought the good of those that sat in darkness. Whatever good we do, it is Christ who does it by us.
18-22. For I will not dare to speak of any—"to speak aught"
of those things which Christ hath not wrought by me—a modest, though somewhat obscure form of expression, meaning, "I will not dare to go beyond what Christ hath wrought by me"—in which form accordingly the rest of the passage is expressed. Observe here how Paul ascribes all the success of his labors to the activity of the living Redeemer, working in and by him.
by word and deed—by preaching and working; which latter he explains in the next clause.