The Apostle Paul desired to express his thankfulness for what God was doing in the lives of the Thessalonian Christians, to defend himself against a slander campaign, to encourage them to stand fast in the face of persecution, and to answer a doctrinal question regarding the fate of Christians who had already died prior to the Lord’s return.
Two key words/phrases stand out: “sanctification” (4:3, 4, 7) and “the Coming of the Lord”, which is referred to in each chapter of this letter (1:10; 2:19; 3:13; 4:15; 5:23). Chapters 4-5 stand out for their teaching on the events surrounding the return of Christ, the rapture of the Church, and the “Day of the Lord”.
Here is an outline of I Thessalonians:
I. The Past: The Work of Faith (1:1-3:13)
II. The Present: The Labor of Love (4:1-12)
III. The Prospective: the Endurance of Hope (4:13-5:28)