Romans 1:16

Paul here enters upon a large discourse of justification, in the latter part of this chapter laying down his thesis, and, in order to the proof of it, describing the deplorable condition of the Gentile world. His transition is very handsome, and like an orator: he was ready to preach the gospel at Rome, though a place where the gospel was run down by those that called themselves the wits; for, saith he, I am not ashamed of it, Rom 1:16. There is a great deal in the gospel which such a man as Paul might be tempted to be ashamed of, especially that he whose gospel it is was a man hanged upon a tree, that the doctrine of it was plain, had little in it to set it off among scholars, the professors of it were mean and despised, and every where spoken against; yet Paul was not ashamed to own it. I reckon him a Christian indeed that is neither ashamed of the gospel nor a shame to it. The reason of this bold profession, taken from the nature and excellency of the gospel, introduces his dissertation. I. The proposition, Rom 1:16, Rom 1:17. The excellency of the gospel lies in this, that it reveals to us, 1. The salvation of believers as the end: It is the power of God unto salvation.

— Matthew Henry's Concise Commentary (public domain)

For I am not ashamed of the gospel--(The words, "of Christ," which follow here, are not found in the oldest and best manuscripts). This language implies that it required some courage to bring to "the mistress of the world" what "to the Jews was a stumbling-block and to the Greeks foolishness" (Co1 1:23). But its inherent glory, as God's life-giving message to a dying world, so filled his soul, that, like his blessed Master, he "despised the shame." for it is the power of God unto salvation to every one that believeth--Here and in Rom 1:17 the apostle announces the great theme of his ensuing argument; SALVATION, the one overwhelming necessity of perishing men; this revealed IN THE GOSPEL MESSAGE; and that message so owned and honored of God as to carry, in the proclamation of it, GOD'S OWN POWER TO SAVE EVERY SOUL THAT EMBRACES IT, Greek and Barbarian, wise and unwise alike.

— Jamieson-Fausset-Brown Commentary (public domain)