During his second missionary tour (Ac 17), Paul came to
Thessalonica and preached the Good News there with no little
success. The city--which had had its name given it by Cassander,
after his wife, the sister of Alexander the Great--was the most
populous in Macedonia, besides being a "free city" and the seat
of the Roman pro-consular administration. Its modern name is
Saloniki.
Very soon the unbelieving Jews stirred up the mob against
Paul and Silas, and dragged Jason before the magistrates. Hence
the brethren sent the missionaries away by night to Beroea, being
alarmed for their safety. As the Apostle was naturally anxious
about the persecuted flock which he had been obliged to leave
behind, he made two attempts to return to them, but these being
frustrated (1Th 2:18), he then sent Timothy, from Athens, to
inquire after their welfare and encourage them.
The report brought back was on the whole satisfactory,
but left occasion for the self-defence, the warnings and the
exhortations of this Letter, which was then sent from Corinth,
probably in 53 A.D.