Commentary of Charles Spurgeon, Adam Clarke & Matthew Henry
Paul, a servant of Jesus Christ, 
called to be an apostle,
separated unto the gospel of God,
(Which he had promised afore by His prophets in the holy scriptures,) Concerning His Son Jesus Christ our Lord,
which was made of the seed of David according to the flesh;
And declared to be the Son of God with power,
according to the spirit of holiness,
by the resurrection from the dead:
By whom we have received grace and apostleship,
for obedience to the faith among all nations, for His name: Among whom are ye also the called of Jesus Christ:
To all that be in Rome, beloved of God, called to be saints:
Grace to you and peace from God our Father, and the Lord Jesus Christ.
Vs.1-7
The Tractation, or setting forth of the main subject, including two sections:
Dogmatic, or what relates to doctrine.
Paraenetic, or what relates to the necessity and importance of the virtues and duties of the Christian life.
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.
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 antiquity of it. It was promised before - 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.
Separated unto the Gospel - Set apart and appointed to this work, and to this only.
Which he had promised afore - Both in the
law and in the prophets God showed his purpose to introduce into the
world a more perfect and glorious state of things; which state was to
take place by and under the influence of the Messiah, who should bring
life and immortality to light by His Gospel.
His human nature: Made of
the seed of David.
His divine nature: Declared to be the Son of God.
According to the spirit of holiness - To me it seems that the apostle simply means that the person called
Jesus was the Son of God, the very Messiah promised
before in the holy Scriptures; and that He was this Messiah was amply
demonstrated.
1st, By His resurrection from the dead.
2nd, He was proved to be the Son of God, the promised
Messiah, by the Holy Spirit, (called here the spirit of holiness), which He sent down upon his apostles, and not on them only, but on all that
believed on his name.
He is the Son of God. The
great proof or demonstration of this is His resurrection from the dead.
Called to be saints - Invited to become
holy persons, by believing the Gospel and receiving the gifts of the
Holy Ghost were formed into a Christian Church.
Observe the description here given of the Christian profession: it is obedience
to the faith. It does not consist in a notional knowledge but in obedience.
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.
