Which part of Scripture is most directly written to the position of the church age believer?

Les teaches that all these letters of Paul are called the church epistles, but Ephesians, Philippians, Colossians, and Philemon are normally referred to as the prison epistles because they were written while Paul was in prison in Rome, shortly before he was martyred. In these prison epistles, there is no single mention of the Old Testament, not a reference back to it, and not one single reference to the Jew, because everything has now flowed into the teaching of the Body of Christ, in which there is no distinction. There is no Jew and no Gentile so far as a division of their background; all have become one as members of the Body of Christ. Les emphasizes that as we study these prison epistles, this is strictly church ground, and no other portion of Scripture is so profoundly directed to the position of the church age believer. You will not find these things in the Old Testament, the four Gospels, or Acts, and even in Paul’s letters of Romans and Corinthians there is not this emphasis on our position in Christ. In just six chapters, ninety-some times, the prepositional phrase “in Him,” “in Christ,” “in Whom” appears, all depicting our position.