Paul wrote this letter to the Thessalonians from Corinth a short time after preaching there on his second missionary journey. There had been a great deal of persecution of the believers that began while Paul was still there. Apparently a group of violent men had decided that it was their responsibility to destroy this new movement. They were, in actuality, afraid of it and how it might change their evil lives. It is often the case that opposition is based on fear and misunderstanding, rather than on reason. Had these men thought about it, it would have been to their advantage as well as to the advantage of their city to have Christianity there. At any rate, Paul had traveled on, having been run off from Thessalonica, and ended up in Corinth. Then he sent Timothy back to find out how things were going. The good news that all was well was a great relief to him, prompting him to write. He thanked them for their concern for him and went on to straighten out some misunderstandings over doctrine that had arisen.

Paul began his letter by commending the church for their spiritual activity and witness. What they were doing was being talked about in other places and was a good example for others to follow. In this they were following Paul's good example, who in turn, was following the Lord. Paul was aware of how difficult it is to remain faithful, especially in the midst of heavy persecution, and was deeply thankful to God for the way they were continuing in their commitment. He reminded them that Jesus not only delivered us from our sins, but will deliver us from all evil when he returns again.
Paul continued this theme by speaking about his own ministry and how it was for him. He, too, had been persecuted so he understood what they were going through. Others, too, had suffered for Christ, notably, the believers in Judea (the land of Israel). It had never been easy to be a Christian, and Paul wanted to share his confidence with these new followers of the Lord. He spoke in a very personal way, telling them that his care for them was like that of a nurse for her children or a father for his sons. In all of this there was the practical intent of helping the Thessalonians live a better life.
A special problem regarding marriage and personal holiness had arisen, so Paul dealt specially with that. The ancient world was notoriously lax in such matters, creating severe problems for those who were trying to keep everything in the proper places in their lives. With the grace and strength of God, Paul said, they would be able to overcome those temptations and obstacles to Christian growth.
Paul spent the last part of his letter discussing a serious misunderstanding that had arisen about the second coming of Jesus. It is difficult to know exactly what the problem was, but it evidently took two forms. First, some people were confused about who would benefit by Christ's return, assuming that only the living would be included. Those who died before Jesus came back would simply be left out. Second, others were worried about when Christ would come back, to the point of no longer working; they became a burden on the rest of the church. Paul set those two problems straight and went on to stress the fact of Christ's return and what that should mean to us. It is a certainty that will terminate this age, bringing comfort to believers and judgment to unbelievers. We are to live expectantly, joyfully, and courageously in the light of its near occurrence.