Who did Paul write to?
Paul wrote to Gentiles, specifically Gentile believers, people not under the Law but under grace. Unlike the Old Testament prophets who wrote to the nation of Israel under Law, Paul addresses those who are members of the Body of Christ. In 1 Corinthians 15 he says he shows Gentile believers a mystery.
Les explains that the Old Testament prophets were writing to the Jew, the nation of Israel under the Law. But when we come into Paul, he is writing to Gentiles who are not under the Law; they are under grace, under a whole different economy, and are now members of the Body of Christ. In 1 Corinthians 15, Paul says he shows Gentile believers a mystery: they shall not all sleep, but they shall all be changed.