Paul, Silvanus, and Timothy, to the assembly of the Thessalonians in God the Father and the Lord Jesus Christ: Grace to you and peace from God our Father and the Lord Jesus Christ.
Thessalonians in God ...  Other Thessalonians were in darkness, in sin, in the "world" and in a state of alienation from God, but these were in the true and Almighty God. This expression identifies "the assembly in Thessalonica as non-heathen," and the addition of "and the Lord Jesus Christ" designates them "as non-Jewish."[2] Practically all of the Thessalonian converts had been won out of paganism  (1 Thessalonians 1:9).