Christian teaching: He has saved us and called us to a holy life—not because of anything we have done but because of his own purpose and grace. 2 Timothy 1:9

The apostle Paul in his second epistle to Timothy wrote about one of the most important mysteries of the Christian faith, the mystery of grace, the mystery by which some are called to do a particular task to build the Kingdom of God, the empire or dominion of the divine perfections, in the world, the spiritual doctrine and the new way of living taught by Jesus for the salvation of humanity.
And on this subject, the Apostle Paul was able to put in his letters the example of his life, since from being a persecutor of Christians, he went through a divine vision of the Lord on one of his trips to the city of Damascus, to being one of the greatest Christian theologians and a great disseminator of the faith in the pagan world, Jesus, in his mercy (compassion, kindness, gentleness), had called him.
The second epistle to Timothy is perhaps the last letter written by Paul, while he was already in the city of Rome, where he was taken to be judged by the Roman emperor; in this letter, Paul sent his dear co-worker Timothy the final exhortations to administer the churches assigned to his care. And in particular, in this epistle, Paul delved deeper into the theme of faith, a faith called to bear fruit in the lives of believers: "For God has not given us a spirit of timidity, but of power and love and discipline" 2 Timothy 1:7.
But Paul expressed in his writing that he also knew that the Christian faith was also a faith in crisis, because as a preacher he had to face a hard test, his martyrdom, as Stephen, the first martyr of the faith, suffered it. And so with these words, he encouraged Timothy to persevere: "Join with me in suffering for the gospel, by the power of God" 2 Timothy 1:8. This is why Paul reminded Timothy that the Lord has a plan since eternity, and that the mystery of grace is born from it, a grace that is not born from works but from the free love of God towards his creatures, human beings. And Paul with devotion referred to the free grace with these words: "He has saved us and called us to a holy life—not because of anything we have done but because of his own purpose and grace" 2 Timothy 1:9. Grace is then, according to Paul's thought, that invitation that Jesus makes to men to live the divine mysteries.