Christ, the Heart of the Gospel
Paul introduces himself as a slave of Jesus Christ. In Roman society, where slaves were not even regarded as human, this was a position he chose for himself: a place with no way of escape and no life of his own. What he proclaims is that the Messiah, foretold by the prophets over long ages, came from the line of David and rose from the dead. This is Christ, the heart of the gospel.
The law cannot save anyone. The more one strives to keep its 613 commandments, the more sin only piles up, and the blood of bulls and goats does not take sin away. Like a guardrail, the law is simply a warning that to leave this road is to die. Salvation is heeding that warning and believing in Christ, who is the safe way.
The names of those God has chosen have been written in the book of life since before the creation of the world. If God has called someone, he called that person because he needed them, so the called must look honestly at the life they are now living by their own free will. To remain in Christ whatever the temptation, as Paul did, is faith; it is obedience; it is salvation.