In this paragraph we have,
I. The person who writes the epistle described (Rom 1:1): Paul, a servant of Jesus Christ; this is his title of honour, which he glories in, not as the Jewish teachers, Rabbi, Rabbi; but a servant, a more immediate attendant, a steward in the house. Called to be an apostle. Some think he alludes to his old name Saul, which signifies one called for, or enquired after: Christ sought him to make an apostle of him, Act 9:15. He here builds his authority upon his call; he did not run without sending, as the false apostles did; klētos apostolos - called an apostle, as if this were the name he would be called by, though he acknowledged himself not meet to be called so, Co1 15:9. Separated to the gospel of God. The Pharisees had their name from separation, because they separated themselves to the study of the law, and might be called aphōrismenoi eis ton nomon; such a one Paul had formerly been; but now he had changed his studies, was aphōrismenos eis to Euangelion, a gospel Pharisee, separated by the counsel of God (Gal 1:15), separated from his mother's womb, by an immediate direction of the Spirit, and a regular ordination according to that direction (Act 13:2, Act 13:3), by a dedication of himself to this work. He was an entire devotee to the gospel of God, the gospel which has God for its author, the origin and extraction of it divine and heavenly.
II. Having mentioned the gospel of God, he digresses, to give us an encomium of it.
1. The antiquity of it. It was promised before (Rom 1:2); it was no novel upstart doctrine, but of ancient standing in the promises and prophecies of the old Testament, which did all unanimously point at the gospel, the morning-beams that ushered in the sun of righteousness; this not by word of mouth only, but in the scriptures.
2. The subject-matter of it: it is concerning Christ, Rom 1:3, Rom 1:4. The prophets and apostles all bear witness to him; he is the true treasure hid in the field of the scriptures. Observe, When Paul mentions Christ, how he heaps up his names and titles, his Son Jesus Christ our Lord, as one that took a pleasure in speaking of him; and, having mentioned him, he cannot go on in his discourse without some expression of love and honour, as here, where in one person he shows us his two distinct natures. (1.) His human nature: Made of the seed of David (Rom 1:3), that is, born of the virgin Mary, who was of the house of David (Luk 1:27), as was Joseph his supposed father, Luk 2:4. David is here mentioned, because of the special promises made to him concerning the Messiah, especially his kingly office; Sa2 7:12; Psa 132:11, compared with Luk 1:32, Luk 1:33. (2.) His divine nature: Declared to be the Son of God (Rom 1:4), the Son of God by eternal generation, or, as it is here explained, according to the Spirit of holiness. According to the flesh, that is, his human nature, he was of the seed of David; but, according to the Spirit of holiness, that is, the divine nature (as he is said to be quickened by the Spirit, Pe1 3:18, compared with Co2 13:4), he is the Son of God. The great proof or demonstration of this is his resurrection from the dead, which proved it effectually and undeniably. The sign of the prophet Jonas, Christ's resurrection, was intended for the last conviction, Mat 12:39, Mat 12:40. Those that would not be convinced by that would be convinced by nothing. So that we have here a summary of the gospel doctrine concerning Christ's two natures in one person.
3. The fruit of it (Rom 1:5); By whom, that is, by Christ manifested and made known in the gospel, we (Paul and the rest of the ministers) have received grace and apostleship, that is, the favour to be made apostles, Eph 3:8. The apostles were made a spectacle to the world, led a life of toil, and trouble, and hazard, were killed all the day long, and yet Paul reckons the apostleship a favour: we may justly reckon it a great favour to be employed in any work or service for God, whatever difficulties or dangers we may meet with in it. This apostleship was received for obedience to the faith, that is, to bring people to that obedience; as Christ, so his ministers, received that they might give. Paul's was for this obedience among all nations, for he was the apostle of the Gentiles, Rom 11:13. Observe the description here given of the Christian profession: it is obedience to the faith. It does not consist in a notional knowledge or a naked assent, much less does it consist in perverse disputings, but in obedience. This obedience to the faith answers the law of faith, mentioned Rom 3:27. The act of faith is the obedience of the understanding to God revealing, and the product of that is the obedience of the will to God commanding. To anticipate the ill use which might be made of the doctrine of justification by faith without the works of the law, which he was to explain in the following epistle, he here speaks of Christianity as an obedience. Christ has a yoke. "Among whom are you, Rom 1:6. You Romans in this stand upon the same level with other Gentile nations of less fame and wealth; you are all one in Christ." The gospel salvation is a common salvation, Jde 1:3. No respect of persons with God. The called of Jesus Christ; all those, and those only, are brought to an obedience of the faith that are effectually called of Jesus Christ.
III. The persons to whom it is written (Rom 1:7): To all that are in Rome, beloved of God, called to be saints; that is, to all the professing Christians that were in Rome, whether Jews or Gentiles originally, whether high or low, bond or free, learned or unlearned. Rich and poor meet together in Christ Jesus. Here is, 1. The privilege of Christians: They are beloved of God, they are members of that body which is beloved, which is God's Hephzibah, in which his delight is. We speak of God's love by his bounty and beneficence, and so he hath a common love to all mankind and a peculiar love for true believers; and between these there is a love he hath for all the body of visible Christians. 2. The duty of Christians; and that is to be holy, for hereunto are they called, called to be saints, called to salvation through sanctification. Saints, and only saints, are beloved of God with a special and peculiar love. Klētois hagiois - called saints, saints in profession; it were well if all that are called saints were saints indeed. Those that are called saints should labour to answer to the name; otherwise, though it is an honour and a privilege, yet it will be of little avail at the great day to have been called saints, if we be not really so.
IV. The apostolical benediction (Rom 1:7): Grace to you and peace. This is one of the tokens in every epistle; and it hath not only the affection of a good wish, but the authority of a blessing. The priests under the law were to bless the people, and so are gospel ministers, in the name of the Lord. In this usual benediction observe, 1. The favours desired: Grace and peace. The Old Testament salutation was, Peace be to you; but now grace is prefixed - grace, that is, the favour of God towards us or the work of God in us; both are previously requisite to true peace. All gospel blessings are included in these two: grace and peace. Peace, that is all good; peace with God, peace in your own consciences, peace with all that are about you; all these founded in grace. 2. The fountain of those favours, from God our Father, and the Lord Jesus Christ. All good comes, (1.) From God as a Father; he hath put himself into that relation to engage and encourage our desires and expectations; we are taught, when we come for grace and peace, to call him our Father. (2.) From the Lord Jesus Christ, as Mediator, and the great feoffee in trust for the conveying and securing of these benefits. We have them from his fulness, peace from the fulness of his merit, grace from the fulness of his Spirit.

Paul, a servant of Jesus Christ - The word δουλος, which we translate servant, properly means a slave, one who is the entire property of his master; and is used here by the apostle with great propriety. He felt he was not his own, and that his life and powers belonged to his heavenly owner, and that he had no right to dispose of or employ them but in the strictest subserviency to the will of his Lord. In this sense, and in this spirit, he is the willing slave of Jesus Christ; and this is, perhaps, the highest character which any soul of man can attain on this side eternity. "I am wholly the Lord's; and wholly devoted in the spirit of sacrificial obedience, to the constant, complete, and energetic performance of the Divine will." A friend of God is high; a son of God is higher; but the servant, or, in the above sense, the slave of God, is higher than all; - in a word, he is a person who feels he has no property in himself, and that God is all and in all.
Called to be an apostle - The word αποστολος, apostle, from αποστελλειν, to send, signifies simply a messenger or envoy; one sent on a confidential errand: but here it means an extraordinary messenger; one sent by God himself to deliver the most important message on behalf of his Maker; - in a word, one sent by the Divine authority to preach the Gospel to the nations. The word κλητος, called, signifies here the same as constituted, and should be joined with αποστολος, as it is in the Greek, and translated thus: Paul, a servant of Jesus Christ, constituted an apostle, etc. This sense the word called has in many places of the sacred writings; e. g. Behold what manner of love the Father hath bestowed on us, that we should be called, κληθωμεν, Constituted, or made the sons of God. As it is likely that no apostle had been employed in founding the Church of Rome, and there was need of much authority to settle the matters that were there in dispute, it was necessary he should show them that he derived his authority from God, and was immediately delegated by him to preach and write as he was now doing.
Separated unto the Gospel - Set apart and appointed to this work, and to this only; as the Israelites were separate from all the people of the earth, to be the servants of God: see Lev 20:26. St. Paul may here refer to his former state as a Pharisee, which literally signifies a separatist, or one separated. Before he was separated unto the service of his own sect; now he is separated unto the Gospel of God. On the word Gospel, and its meaning, see the preface to the notes on St. Matthew; and for the meaning of the word Pharisee, see the same Gospel, Mat 3:7 (note).

Paul, a servant of Jesus Christ,.... The name of the author of this epistle is Paul, who formerly was called Saul. Some think his name was changed upon his own conversion; others, upon the conversion of the Roman deputy Sergius Paulus, Act 13:7; others, that he was so called from the littleness of his stature; but rather it should seem that he had two names, which was usual with the Jews; one by which they went among the Gentiles, and another by they were called in their own land; See Gill on Act 13:9. "A servant of Jesus Christ"; not a servant of sin, nor of Satan, nor of man, nor of Moses and his law, nor of the traditions of the elders, but of Jesus Christ; and not by creation only, but by redemption, and by powerful efficacious grace in conversion; which is no ways contrary to true liberty; nor a disgraceful, but a most honourable character; and which chiefly regards him as a minister of the Gospel:

called to be an apostle: an apostle was one that was immediately sent by Christ, and had his authority and doctrine directly from him, and had a power of working miracles from him, in confirmation of the truth of his mission, authority, and doctrine; all which were to be found in the author of this epistle, who did not thrust himself into this office, or take this honour to himself, of which he always judged himself unworthy, but was "called" to it according to the will, and by the grace of God:

separated unto the Gospel of God. This may regard either God's eternal purpose concerning him, his preordination of him from eternity to be a preacher of the Gospel, to which he was separated from his mother's womb, Gal 1:15; or the separation of him to that work made by the order of the Spirit of God, Act 13:2. The phrase used is either in allusion to the priests and Levites, who were separated from their brethren the children of Israel, to their sacred employments; or rather to the apostle's having been "a Pharisee", which signifies "one separated", as he was now; only with this difference, before he was separated to the law, but now "to the Gospel", to preach and defend it, which he did with all faithfulness and integrity; the excellency of which Gospel is signified by its being called "the Gospel of God": he is the author of it; his grace is the subject of it; and he it is who commits it to men, qualifies them for the preaching of it, and succeeds them in it.