Probably the oldest surviving Christian document. It was written to a congregation worried that members who had died would miss what was coming, and it answers that worry in about two paragraphs.
What the book is
1 Thessalonians is a short letter of encouragement to a young congregation Paul had left in a hurry. It reviews his time with them, defends his conduct, reports relief at good news brought back by Timothy, gives ethical instruction, and answers a specific pastoral question about believers who had died.
There is no sustained controversy in it and no argument against opponents inside the church. It reads as a letter written to reassure.
How it is put together
Chapters 1 to 3 are almost entirely retrospective — what happened when Paul was there, what happened after he left, what Timothy reported. Chapters 4 and 5 are instruction, including the passage about those who have fallen asleep and the following material about times and seasons.
The thanksgiving section is unusually long, running through three chapters, which is one reason the letter’s structure gets discussed.
The dating question
This is one of the firmest dates in the New Testament, and it rests on the same external anchor as the rest of Paul.
Acts places Paul in Corinth before the proconsul Gallio, and the Delphi inscription — a letter of Claudius naming Gallio as proconsul of Achaia — dates that governorship to around 52 CE. 1 Thessalonians was written from Corinth shortly after Timothy returned from Thessalonica, which puts it around 50 to 51 CE.
That makes it, on the majority view, the earliest surviving Christian writing of any kind — earlier than any gospel, and earlier than the letter that carries the Christ hymn.
Where the external record touches it
Thessalonica supplies one of the better-known cases of an incidental detail being confirmed. Acts 17 calls the city’s magistrates by a specific term, politarchs, which is not the usual word for civic officials elsewhere and was once cited as an error. Inscriptions from Thessalonica and the surrounding region have since attested the title repeatedly, in the right period and the right place.
It is worth being precise about what that establishes. It shows that the writer of Acts used the correct local term for a Macedonian city’s magistrates, which is evidence of familiarity with the setting. It is not evidence that any event in Acts 17 happened, and treating it as such is a common overreach.
The city has been continuously occupied since antiquity, which limits excavation, but its epigraphic record is substantial.
A note on how it reads
The passage in chapter 4 about the dead is the most quoted part of the letter and the most often read out of context. The question it answers is narrow and local: the Thessalonians expected something imminent, some of them had died, and they wanted to know whether those people had missed it. Paul’s answer is that they had not.
Reading that passage as a timetable rather than as an answer to that question is the interpretive move this site is most often asked about, and it is worth noticing that the letter itself declines to give a timetable a paragraph later.
Related: 2 Thessalonians and the overview of Acts.