The apostle Paul, following the thought of master Jesus, preached the doctrine of the Kingdom of God, the dominion or empire of God's perfections, as a faith or a spiritual revelation of mysteries, a truth that Paul did not forget to teach in his letter addressed with great devotion to the first Christians of the city of Rome. Presenting a new religion as a doctrine of mysteries was very common in those times, as also occurred with Gnosticism, which preached that only through a mysterious Gnosis could the knowledge of the truth be achieved.
In the Christian faith, as Paul taught in his letter to the Romans, the knowledge of Jesus can only be achieved by rejecting the desires of the flesh and accepting the life according to the spirit, because reason deceives man and prevents him from seeing his true purpose in life, to achieve the excellence of Jesus: "Be merciful, as your Father is merciful" Luke 6:36.
Ultimately, Jesus is that mystery that men must strive to reveal, because there is a knowledge that is there but that due to its subtle nature needs grace to be understood, as Jesus taught in the parable of the hidden treasure or the pearl of great price. The Christian faith is ultimately a progressive spiritual growth towards the spiritual gift of eternal life, the life that once obtained cannot be lost, this is the true blessedness of the adult Christian, as Paul taught with wise words: "You have been set free from sin and have become slaves of God, the benefit you reap leads to holiness, and the result is eternal life" Romans 6:22.
It is for all this that Paul, at the end of his epistle to the Romans, made a final reflection, explaining how this mysterious knowledge of the Lord was only revealed at the end of the times designated by the Father so that humanity would know a new covenant with God: "Now to him that is of power to stablish you according to my gospel, and the preaching of Jesus Christ, according to the revelation of the mystery, which was kept secret since the world began" Romans 16:24-25.