Two letters that Paul wrote to the church in Thessalonica are preserved in the New Testament. The first letter — 1 Thessalonians — was written to a community of believers who had been Christians for only a short period of time, probably no more than a few months. We learn from the Book of Acts that during Paul's stay in the city of Thessalonica, he preached in a Jewish synagogue on three successive Sabbath days. He evidently stayed in the city for some time thereafter and continued his work among the Gentiles. Although his ministry was successful to the extent that he won converts to Christianity from both Jews and Gentiles, he did encounter opposition, especially from Jews who resented very much that he was able to win Jewish followers. Because of this opposition, Paul wisely left the city for fear that the newly formed Christian community would be persecuted as he had been. He regretted that he must leave the Christians before they were well established in the faith, but he hoped that he might visit them again in the near future. When sickness prevented him from returning, he sent his colleague Timothy to strengthen the group and then report back to Paul on the progress that had been made. When Timothy returned to Paul with the good news that the members of the church were standing firm in their new faith, Paul wrote the First Epistle to the Thessalonians.
Paul congratulates the Thessalonians on their fidelity to the gospel that he had proclaimed while among them and urges them to remain steadfast in the faith. He warns them against sensuality and various forms of self-seeking, which are contrary to the spirit of the Christian way of life. But the main purpose of Paul's letter is to deal with a special problem that developed after Paul left the city. Paul shared with the Christians at Thessalonica his belief that the end of the age would come in the very near future. In part an inheritance from Jewish apocalypticism, this belief held that the messianic kingdom would be ushered in by a sudden catastrophic event, at which time the heavenly Messiah would descend on the clouds of heaven with power and great glory. When the first Christians accepted the idea that the man who had died on the cross was the real Messiah, they were convinced that he must return to earth to complete the work that he had begun. The manner of his second coming was conceived in accordance with the apocalyptic conceptions. This belief was common among the early Christians, and Paul accepted it along with the rest. Although the Christians were quite insistent that no one knew the exact time when this second coming would take place, they felt sure that it would occur during the lifetime of those who were then members of the Christian community.
