Theodore of Mopsuestia

For you know, he says, how you came to be chosen (that is, how you arrived at faith), for you did not believe solely by means of our words. Indeed, we not only spoke but also showed wonders, great and glorious and worked by the Spirit, by which you were strengthened with regard to the things we had spoken to you. Hold on tightly to what you have learned, and don’t be deflected from your course by the external things that happen to you.

Paul says that Timothy is coming to strengthen the Thessalonians with his words, stabilizing the thinking of the Thessalonians by his presence with them, lest they collapse under the weight of their tribulations. Paul describes this collapsing as a “commotion,” being caught up in the passions of your persecutors.