The First Epistle of Paul to the Thessalonians, usually referred to simply as First Thessalonians and often written 1 Thessalonians, is a book from the New Testament of the Christian Bible. The first letter to the Thessalonians was likely the first of Paul's letters, probably written by the end of A.D. 52[1], making it, so far as is now known, the oldest extant Christian document.

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. (summary by Wikipedia)