The book of Acts records Paul’s work in Thessalonica with Silas (chapter 17). Paul likely wrote a letter to these believers from Corinth. Scholars are largely in agreement that this letter was written around AD 50 and is the oldest of Paul’s surviving letters.
Paul and Silas had to leave Thessalonica abruptly due to riots caused by jealous Jews (see Acts 17:5-10). They had not been there long, and so the converts were left to fend for themselves, and thus fell prey to influences that undermined Paul and Silas’s work. Paul wrote this letter to encourage and instruct these recent converts in matters of proper conduct in daily life as well as the question of Christ’s second coming.
On the latter point, believers in Thessalonica were concerned that some believers had already died and yet Christ had still not returned. What will happen to those who have died when Christ does return? Paul stresses that Christ’s coming will happen publicly—with a shout and a trumpet—and those who had died will not be forgotten. In fact, they will raised first. No one knows, however, when this will happen. Christ will return like a thief in the night, and so all believers should be alert and self-controlled in the meantime. That way, they will be “kept blameless at the coming of our Lord Jesus Christ” (4:23). For Paul, the future hope does not lead to escapism from this world, but a renewed effort to live daily in a manner consistent with faith in the resurrected Christ.
– Peter Enns