The first letter to the Thessalonians was likely the first of Paul's letters, probably written by the end of A.D. 52, making it, so far as is now known, the oldest extant Christian document (almost all scholars hold that the gospels were written over a decade later). It was written from Corinth after Timothy had returned from Macedonia, relating the state of the church in Thessalonica (). For the most part, the letter is personal in nature, with only the final two chapters spent addressing issues of doctrine, almost as an aside. Paul's main purpose in writing is to encourage and reassure the Christians there. Paul urges them to go on working quietly while waiting in hope for the return of Christ.
The church is believed to have been composed almost exclusively of gentiles. This would reflect the ethnic and religious makeup of Thessalonica, and is supported by Paul's brief remark in 1:9 that they "turned to God from idols," a remark that would have made little sense to make to a Jewish audience.
Paul was concerned because of the infancy of the church. He had only spent a few weeks with them before leaving for Athens. In his concern, he sent his delegate, Timothy, to visit the Thessalonians and to return with a report. While, on the whole, the news was encouraging, it also showed that important misunderstandings existed concerning Paul's teaching of Christianity. Paul devotes part of the letter to correcting these errors, and exhorts the Thessalonians to purity of life, reminding them that their sanctification is God's will for their lives.
The letter is usually outlined as follows:
Paul gives thanks for the news about their faith and love; he reminds them of the kind of life he had lived while he was with them. Paul stresses how honorably he conducted himself, reminding them that he had worked to earn his keep, taking great pains not to burden anyone. He did this, he says, even though he could have used his status as an apostle to impose upon them.
Paul goes on to answer some concerns which have arisen in the church. Notably, there was some confusion regarding the fate of those who die before the arrival of the new kingdom. Many seem to have believed that an afterlife would only be available to those who lived to see the kingdom. Paul explains that the dead will be resurrected, and dealt with prior to those still living. Thus, he assures, there is no reason to mourn the death of fellow Christians, and to do so is to show a shameful lack of faith.
Unlike all subsequent Pauline epistles, 1 Thessalonians does not focus on justification by faith or questions of Jewish-gentile relations, themes that are covered in all other letters. Many scholars see this as an indication that this letter was written before the Epistle to the Galatians, where Paul formed and identified his positions on these matters.
The vast majority of New Testament scholars hold 1 Thessalonians to be authentic, with dissent from this position being minuscule at best. 1 Thessalonians matches other accepted Pauline letters, both in style and in content, and its authorship is also testified to by 2 Thessalonians.
1 Thessalonians 2:13-16 have often been regarded as a post-Pauline interpolation. The following arguments have been based on the content: (1) the contradiction between Romans 9-11 and 1 Thess. 2.14-16. (2) The references to what has happened to Jews as a model for a Gentile Christian church. (3) There were no extensive persecutions of Christians by Jews in Palestine prior to the first Jewish war. (4) The use of the concept of imitation in 1 Thessalonians 2.14 is singular. (5) The aorist eftasen (has overtaken) refers to the destruction of Jerusalem(6) The syntax of 1 Thes 2:13-16 deviates significantly from that of the surrounding context.
It is also sometimes suggested that 1 Thes 5:1-11 is a post-Pauline insertion that has many features of Lukan language and theology that serves as an apologetic correction to Paul's imminent expectation of the parousia in 1 Thes 4:13-18.
Other scholars such as Schmithals, Eckhart, Demke and Munro have developed complicated theories involving redaction and interpolation in 1 and 2 Thessalonians.