How long had God dealt with Israel before Christ came on the scene?
God had been dealing with Israel for over 2,000 years before Christ came on the scene. That extended period was one thing, but God then began dealing with Gentiles in a way that had never been heard of before, revealing the mystery that Christ is in you, the hope of glory.
Les explains that in Colossians 1:27, Paul writes of the riches of the glory of this mystery among the Gentiles. Such statements are not found in the four Gospels, the Old Testament, or the rest of the Bible except Paul's epistles. God had dealt with Israel for over 2,000 years before Christ came, but His current dealing with Gentiles had never been heard of before. This mystery is Christ in you, the hope of glory. Les then connects this to Romans 8:10: if Christ be in you, the body is dead because of sin, since Adam and the flesh were under the curse, and all men must die unless the Lord comes to translate us.
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: