Paul arrived in the Thessalonica after a short time in Philippi (Acts 17:1-9). In Philippi he was arrested illegally and released when he informed the Philippian magistrates he was a Roman citizen. As is typical for Paul he visits the local synagogue and “reasoned from the Scripture” that it was necessary for the Messiah to suffer, die, and rise from the dead. Luke indicates some Jews were persuaded, but also a “large number of God-fearing Gentiles and quite a few prominent women” (Acts 17:4).
First, Paul must defend himself against unnamed opponents who are slandering him. Based on his defense in chapter 2, these opponents acclaim Paul has no divine authority and may be using the local church to enrich himself. It is true Paul was forced to leave Thessalonica under the cover of darkness (Acts 17:10), leaving Jason with some legal and financial burdens (Acts 17:9, Jason posted bail for Paul). Paul says his appeal to his readers did not “spring up from error or impure motives” (2:3) nor did he use the slick rhetoric of the Sophists to trick his readers into believing the Gospel (2:5). The church itself is a witness to Paul’s behavior in Thessalonica, so the opponents have no basis for making these charges.
Second, although Timothy gave an “encouraging report” (1 Thess 3:6-10), he also seems to have reported on two or three problems for the church. In 4:3-8 Paul deals with sexual immorality, encouraging people to control themselves and live in an honorable way. In 4:9-12 Paul instructs the Thessalonican believers to live a “quiet life” and to work to provide for their own needs. It may be the case some members of the congregation were abusing the generosity of others, no longer working while they waiting for the soon arrival of the Lord Jesus. In both of these cases, Paul encourages the readers to live lives which “win the respect of outsiders” (4:12).
Third, Paul addresses some concerns about the return of the Lord (1 Thess 4:13-5:11). Since Paul’s time was cut short, he may not have had the time to answer all the questions the church may have had about the imminent return of Jesus. What is more, some members of the church have died prior to the expected return of the Lord. Paul first must comfort the community by explaining that those who have died in Christ will certainly participate in the resurrection from the dead prior to the return of the Lord. In fact, they will rise first and join those who are still living as they are caught up to meet the Lord in the air (4:15). In chapter 5 Paul points out that the day of the Lord will come unexpectedly, so the “children of light” ought to live their lives in sober anticipation of the return of the Lord. Both of these teachings conclude with “therefore encourage one another.” This is the main point of any teaching on the return of the Lord, encouragement to living godly lives which “win the respect of outsiders” (4:12).
Although 1 Thessalonians is remembered as the “Rapture book” in popular teaching, the main theme of the book is “encourage one another.” Since the Thessalonian church was small and had to endure some pressure from both secular authorities and their cousins in the Jewish synagogue, they may have felt as though their new faith in Jesus was not worth the trouble. The congregation must comfort one another and encourage each member of their small group to continue living out their faith in Jesus as children of God.