For I am not ashamed of the gospel of Christ; for it is the power of God unto salvation to every one that believeth; to the Jew first, and also to the Greek.
The power of God unto salvation - This word means complete deliverance from sin and death. It cannot imply anything less than eternal life. When the apostle declares that it is the power of God unto salvation 'to everyone that believeth,' it implies that all who become believers 'shall be kept by the power of God through faith unto salvation.' 1 Peter 1:5. The apostle thus commences his discussion with one of the important doctrines of the Christian religion, the final preservation of the saints. He is not defending the gospel for any temporary object, or with any temporary hope. He sees in it a plan for the complete and eternal recovery of all those who believe in the Lord Jesus Christ.
To everyone that believeth - Compare Mark 16:16-17. This expresses the condition, or terms. It is only to those who confide or trust in it. If this qualification is met, it bestows its blessings freely and fully.
To the Jew first - to them had been committed the oracles of God; the Messiah had come through them; they had had the Law, the temple, and the service of God. 'It was necessary that the Word of God should first have been spoken to you; but seeing ye put it from you, and judge yourselves unworthy of everlasting life, lo, we turn to the Gentiles.' Compare Matthew 21:43.
And also to the Greek - To all who were not Jews, that is, to all the world. It was not confined in its intention or efficacy to any class or nation of people. It was adapted to all, and was designed to be extended to all.
Barnes Notes on the Bible:
Paul introduces himself as a servant of Jesus Christ, separated unto the gospel of God promised afore by his prophets in the holy scriptures concerning his Son Jesus Christ, who was made of the seed of David.
Paul declares the gospel consistent with all that had been declared in the Jewish dispensation. He was anxious to show that his doctrine coincided with the Old Testament. That it was 1) Confirmed by the authority of inspired men 2) Built upon the inspired writings of prophets.
His aim was to disarm their prejudice and furnish proof of the truth, 'saying none other things than those which the prophets and Moses did say should come.' Acts 26:22-23
He appeals and defends every point by the authority of the Old Testament. He never undervalued it or regarded it as obsolete. Every passage he cites is proof that it is from God.