There are two possible meanings for the word church (ἐκκλησία) here: it could refer to (a) the people who comprise the church in Thessalonica—i.e., all the baptized people in that city; or (b) an actual gathering of those people. The first meaning would be favoured by a comparison with 1 Corinthians 1:2 and 2 Corinthians 1:1, where Paul addresses the church of God in Corinth, and where he is clearly addressing people as such, rather than a particular gathering of those people. There are, however, three reasons for accepting the second meaning in this case:

1. It is noteworthy that here in verse 1, Paul writes not “to the church of God in Thessalonica,” but “to the church of the Thessalonians,” an expression not found anywhere else in the Pauline letters except 2 Thessalonians 1:1.

2. The Thessalonian Christians would have been very familiar with the citizen assembly (called an ἐκκλησία) since it was very much a part of their lives.

3. The Thessalonian believers would not have received printed copies of Paul’s letter as would be the case today; they would have heard it being read to them when they were gathered together as believers (see 1 Thessalonians 5:27).¹

We can therefore imagine the Thessalonian believers gathered together listening to this letter being read out to them.