Do the prison epistles reference the Old Testament, and why?
No, the prison epistles—Ephesians, Philippians, and Colossians—do not reference the Old Testament. This omission is purposeful because God is dealing with the whole human race on one level, bringing Jew and Gentile together into one Body with no difference, so the old Jew-Gentile demarcation is no longer in view.
Les teaches that once we get into the prison epistles and these higher or deeper church truths, God is no longer concerned with the demarcation between Jew and Gentile, because He is now dealing with the whole human race on one level. Every person who is saved comes into the Body of Christ on the same level, whether Jew or Gentile, and the Jew has lost his identity so far as the Church Age is concerned. In Ephesians, Philippians, and Colossians, there is no dividing between Jew and Gentile, and there is no reference to the Old Testament. That is all for a purpose: God is no longer making any reference to the Jew or to the Old Testament, and it is for His own purposes. Les also stresses that people must get out of the four Gospels and into Paul's writings, because the four Gospels are still 90% Jewish and have been set aside in God's program, though that does not mean throwing them away any more than throwing away the Old Testament. These things must be kept in the perspective of the unfolding and progressive revelation even of Paul's letters.