INTRODUCTION TO THE SECOND LETTER TO THE THESSALONIANS
Paul wrote this letter from Corinth, not long after his first letter to the Thessalonians, probably near the close of 53 A.D. We have no way of knowing all that happened between the writing of the two letters. But Paul learned just how the church was progressing, and he saw some things which required immediate attention. Some things were no longer a problem, such as their fears about those who had died, and their possible weakening under persecution. But some were teaching that the Day of the Lord had already come (2 Thessalonians 2:2-3). Such speculation led some to be lazy loafers, and much of chapter 3 is directed toward that problem.
The purpose of this letter is to: (1) thank them and praise them for their faith; (2) to inspire them to continue to be strong in the faith; (3) to correct wrong ideas about the Day of the Lord; (4) to discipline the lazy loafers in the church, and to remind the church of its responsibilities toward such as these.
The Introduction to First Thessalonians gives more detail on the church and its planting.