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:  To God only wise, be glory through Jesus Christ for ever. Amen.
Romans 16:25-27

These verses are a doxology to the Lord. Words of a hymn or praise to Him. What about the mystery? There is the revelation of the mystery, and that revelation is how the Gentiles can be saved by God, only partly, and mostly the whole counsel of God.

There is much in the Gospel of Jesus Christ that is revealed to us through the knowing of Christ such as the Incarnation of God – God became flesh and dwelt among us, The Trinity – the Holy Triune God. God becoming Man that He might die for His enemies, then to be buried, then to prove it all He is raised from the grave, which proves that all that He said, and taught is truth (Romans 1:4). It also proves all the words of Moses, the prophets, and the wisdom books of the Old Testament.

I am thankful that He has revealed Himself to me through His Spirit, by the Old and New Testaments.

If you will call on the name of Jesus through faith, believing that He died for your sins, was buried, and He rose from the dead you will be saved (Romans10:9-10).