The phrase in God the Father
is not easy to interpret. It is common for Paul to speak about believers being in Christ
(see, e.g., Ephesians 1:3–14), thus indicating their union with Christ and the fact that every blessing in the Christian life flows out of that union. But the phrase in God
is virtually without parallel in the rest of Paul’s writings. Yet its main thrust is clear: everything that the Thessalonian believers are and have comes from God. God is to be thanked for their faith, love, and hope, their labour and their endurance (1 Thessalonians 1:2–3); they are his because he chose them, not because Paul, Silvanus, and Timothy persuaded them (1 Thessalonians 1:5); and they will be fully sanctified because God is faithful (1 Thessalonians 5:23–24).1,2
1 Paul, Silvanus, and Timothy,To the church of the Thessalonians in God the Father and the Lord Jesus Christ: Grace to you and peace.