The building of God has a foundation. Paul called himself the “wise master builder, who has laid the foundation: Jesus Christ.
"According to the grace of God which is given unto me, as a wise masterbuilder, I have laid the foundation, and another buildeth thereon. But let every man take heed how he buildeth thereupon." 1 Cor. 3:10
Paul called this “my gospel” in Romans.
"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,
But now is made manifest, and by the scriptures of the prophets, according to the commandment of the everlasting God, made known to all nations for the obedience of faith." ROM 16:25-26
At the time of Paul’s writings, there were the scriptures of the prophets, which testified to the sufferings of Christ and the glories to follow (1 Peter 5:1).
"The elders which are among you I exhort, who am also an elder, and a witness of the sufferings of Christ, and also a partaker of the glory that shall be revealed." 1 Peter 5:1
However, Paul came to reveal a new body of truth called the “mystery which was kept secret since the world began”. The revelation of the mystery is the foundation of the and there is no other foundation that can be laid but that of Christ Jesus.”
"Even the mystery which hath been hid from ages and from generations, but now is made manifest to his saints:
To whom God would make known what is the riches of the glory of this mystery among the Gentiles; which is Christ in you, the hope of glory." Col 1:26-27
Read the book Here ???? Christ As Righteousness Sanctification and Reward