This comment calls to mind Paul’s statement in 1 Thessalonians 1:5 that his gospel came to the Thessalonians with power and with the Holy Spirit; it also reminds them that God continues to work in them by his word. The nature and effect of that working are not specified here, but the rest of the letter does give some indication of what it is. It must surely include their work produced by faith,
their labor prompted by love,
and their endurance inspired by hope
(1 Thessalonians 1:3), as well as the brotherly love which Paul commends in 1 Thessalonians 4:9.
13 And we also thank God constantly for this, that when you received the word of God, which you heard from us, you accepted it not as the word of men but as what it really is, the word of God, which is at work in you believers.