The Apostle Paul wrote this letter (epistle) in accordance with the information that God and the Lord Jesus Christ revealed to him.
Romans 1:1 and 2:
1:1Paul, a slave of Christ Jesus, called, an apostle, having been separated2 into God's good-message, .2which He promised-beforehand by means of His prophets in holy writings,
Paul begins this letter by first identifying himself by name (Paul) to those to whom he is writing. Then he identifies himself by 'job-title' or 'work-function' relative-to his working/service relationship with Christ Jesus.
Paul was a slave, bound to serve Christ Jesus, his Master as regards his work being a holy-person. This service as a slave meant that his whole being was at the service of, in service to – Christ Jesus. Paul carried-out his service by his own freedom of will. Wherever Paul was and whatever he was doing he was to behave as a slave of Christ Jesus, not a slave serving anybody or anything else, even though at times during his life he was physically-bound with physical-chains to soldiers in prison! Even so, Christ Jesus was his Lord, the one whom Paul believed and obeyed and from-whom Paul took his instructions. During Biblical times, a master was obligated to take-care of his slave (bond-servant) and the slave was obligated to do all his master would ask of him. It was a mutually-beneficial relationship between the master and his slave. [Some Greek texts read "slave of Jesus Christ."]
Paul’s standing was that he was “called.” The word "called" could also be translated as "invited" – he was an invited person. He had been issued an invitation by Christ Jesus and he had accepted it. As we read on we will find out what the call (invitation) was and how Paul responded to that invitation.
Paul’s service was to do the work of an apostle. An "apostle" is a person sent-forth or sent-away by someone on a specific mission or assignment to someone else. In the context here, we read that Paul was an apostle of Christ Jesus.
It is clear that Paul had not decided this all by himself, nor was there some "unknown force" driving him to do the things that he was doing, nor was he deluded into thinking that he was somebody else, nor did he decide that he had reached the level of being "good enough" to be an apostle to his neighbors or to the whole world (he was not self-appointed), nor was there a committee involved in this decision, nor had he "forced" God or Jesus Christ into making him an apostle!
Paul, a slave of Christ Jesus, called, an apostle…
Here, Paul is referring to the books of the prophets already written in what is part of the old covenant writings (often referred to as 'old testament'). Much of what these old covenant prophets spoke was recorded in written form, and it concerned the subject matter of the good-message regarding which Paul was an apostle.
[Reference: Acts 9:1-20, 13:2, 22:1-21, and 26:1-23; Romans 8:28, 15:4; I Corinthians 1:1 and 24; Galatians 1:15 and 16, 3:8; Ephesians 4:11-13; I Peter 1:10-12.]
Reading from verse 1:
Verses 1-3(a):
1:1Paul, a slave of Christ Jesus, called, an apostle, having been separated2 into God's good-message, .2which He promised-beforehand by means of His prophets in holy writings, .3concerning His son…
Now we know the subject matter of the good-message regarding which Paul was an apostle – concerning God's son. The prophets of the old covenant had previously spoken and written by revelation from God concerning His son.
[Note: verbs with a superscript 2 (2) immediately following them indicate the "perfect" tense - details are provided in the "Relevant Notes" link of this study.]
or
