Why was God's dealing with the Gentiles such a new thing after 2,000 years of dealing with Israel?

God had been dealing with Israel for over 2,000 years before Christ came, so His direct dealing with Gentiles was unheard of before. This truth belongs to the mysteries revealed in Paul's epistles: the secret among the Gentiles is Christ in you, the hope of glory.

Les explains that the statements about God's dealing with Gentiles are not found in the four Gospels, the Old Testament, or anywhere else in the Bible except Paul's epistles. For over 2,000 years God had dealt with Israel before Christ came, but now His dealing with Gentiles had never been heard of before. This secret among the Gentiles is part of the overall body of truth called the mysteries, and this particular one is that Christ is in you, which gives the hope of glory. Les then connects this to Romans 8:10: if Christ be in you, the body is dead because of sin. The old Adam and the flesh are under the curse; this body will die unless the Lord comes to translate us, all part of the fall of man, that death came in, and so all men have to die.

Colossians 1:27

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:

Why was God dealing with Gentiles such a new thing in the Bible?

God had been dealing with Israel for over 2,000 years before Christ came, so His direct dealings with Gentiles were previously unheard of. The mystery revealed in Paul's epistles—that Christ is in Gentiles, the hope of glory—was absent from the Gospels, the Old Testament, and the rest of Scripture.