1 Thessalonians 4 focuses on instructions for living a holy life and encouragement for believers to continue in their faith until Christ returns. Specifically, it teaches about three key topics:1) Sexual immorality and purity: The Apostle Paul encourages believers to avoid sexual immorality and to pursue purity. He emphasizes that God has called us to holiness and purity, rather than impurity and moral corruption.2) The resurrection of the dead: Paul also teaches about the resurrection of the dead and the return of Jesus Christ. He reminds believers that those who have died in Christ will be raised again and gathered with the living to be with Him forever.3) Being ready for Christ's return: Finally, Paul encourages his readers to live in readiness for Christ's return. He emphasizes the importance of being prepared, active and alert, so that when Christ returns, believers will be ready to meet him.