I think it’s important to notice what Paul is thankful for. He is thankful first for the fact that they received the Word and that action resulted. The action, in turn, resulted in witness and further proclamation of the Word. Within that passage we have an excellent pattern for spreading the gospel.
It is often difficult for us to balance faith and works. That is a good thing, because I don’t think it’s balance we’re looking for. It’s not a proper proportion of faith and works that becomes a recipe for results. Rather, God acts in us by grace, received by faith. God’s grace makes the response of action possible, and the action of God’s grace makes the following witness possible, because the witness must be to what God has been able to do.
Paul is thankful that the Thessalonian believers have become a witness as God has acted through them. God chose them (1:4) because the gospel came to them not just as words but as active power (1:5), which resulted in them imitating those already impacted by the power of the gospel (1:6), which results in them being an example (can we say witness?) to others (1:7), and that, in turn, means that the word of the gospel goes forth from them.
Do you see the generational effect here?
Think: This was successful ministry. In our ministries, when things aren’t working, where is this broken?