Paul, a bondservant of Jesus Christ, called to be an apostle, separated to the gospel of God (Romans 1:1)
As a bondservant of Jesus Christ, Paul referred to his station in life. First and foremost, he was Jesus’ servant.
As a “called apostle” of Jesus Christ, Paul referred to his role as Jesus’ servant. Jesus Himself has specifically chosen Paul for this mission (Acts 26:15-18).
Finally, as one who was “separated to the gospel of God,” Paul referred to the message he lived and proclaimed as a bondservant and apostle of Jesus Christ.
Separated to the gospel of God.
Paul was “separated” or “set apart” for a specific purpose. He was set apart “to” something. Implied within Paul being separated “to” something is that he was also separated “from” something as well.
To and from.
Paul wrote to the Christians in Thessalonica about this same idea.
For they themselves declare concerning us what manner of entry we had to you, and how you turned to God from idols to serve the living and true God, (1 Thessalonians 1:9)
Turning “to God” meant they turned “from idols.” Jesus reminds us that it’s impossible to serve two masters (Matthew 6:24).
It’s also important to notice that it’s not enough just to be separated “from” something - we must also be separated “to” God.
A Christian who is separated from something and not separated unto Christ will have a barren life. His life will be without joy and he will become critical and sometimes cynical. - McGee, Thru the Bible Vol. 4, 646
A new horizon.
The Greek word for “separated” (aphorizō) is interesting because within it, you will notice our word “horizon.” By being “separated to the gospel of God,” Paul is saying he has a totally new outlook on life.
He had been brought up in one circle, and his thinking had been circumscribed by that circle. All of his life had been lived within a horizon that comprehended the total vision which he was able to have from that point.
Now God had saved him. Now he had seen the vision of the Saviour. He had become the bondslave of Jesus Christ. He had obeyed completely, accepting the apostleship unto which God had called him.
Now he had been lifted out of the circle where he had lived and had been put into an entirely different circle. It had a different center and therefore a different horizon. And the new center was so far removed from that in which he had lived before that there was no segments overlapping. He was off-horizoned. He was separated unto the gospel of God. - Barnhouse, Romans Vol. 1, 17
The gospel of God is what gives life. I think of Jesus’ conversation with Nicodemus about the new birth (John 3:3-5) and the Lord’s discussion about how He gives living water with the Samaritan woman (John 4:10-14).
Paul had been set apart and given a new life by the message He proclaimed - God’s gospel. It wasn’t anything Paul had developed. The gospel (or good news) was from God (2 Peter 1:19-21).
The New Testament makes it clear that the gospel is about Jesus (Romans 1:1-3; 15:16, 19; 1 Corinthians 9:12; 2 Corinthians 2:12; 4:4; 1 Thessalonians 3:2).
Paul used counter-imperial language to argue that the happiness Romans attributed to the emperor was only to be found in Jesus, who personified the “good news of God.” This is similar to Philippians 3:20-21, where Jesus’ empire turns out “to be the reality of which Caesar’s empire is the parody.” - Pollard, Truth for Today Commentary, 31-32
What about us?
When we obey the gospel of Christ, we are given a new life (Romans 6:3-4). Having been given a new life - a new “horizon” - the way we live ought to reflect this new life.
We must not try to live our new life in Christ Jesus while clinging to the remnants of our old life of sin. If you’ve been baptized into Christ’s death, then He has set you free from sin (Romans 6:5-7).
Christians are to lead “holy” lives - devoted and set apart to God (1 Peter 1:13-16).