Paul, Silvanus, and Timothy, to the assembly of the Thessalonians in God our Father, and the Lord Jesus Christ:
Archibald Thomas Robertson says, "The word originally meant ’assembly’ as in Acts 19:39, but it came to mean an organization for worship whether assembled or unassembled (cf. Acts 8:3)" (Vol. IV 5). The New English Bible reads, "From Paul, Silvanus, and Timothy to the congregation of Thessalonians who belong to God our Father and the Lord Jesus Christ."