We are bound to thank God always for you, brethren, as it is fitting, because your faith grows exceedingly, and the love of every one of you all toward each other abounds;
All Commentaries on 2 Thessalonians 1:3 Go To 2 Thessalonians 1
Thietland of Einsiedeln
AD 1000
Indeed, we must note that in the first letter he does not say 'we ought to give thanks,' but 'we give thanks.' For truly there is a greater virtue in what he says, 'we ought to give thanks,' because indeed somebody can freely give thanks for some thing; but truly he who says that he ought, shows that he, too, is a debtor. Therefore the Apostle shows that he, too, is a debtor.
because your faith is increasing greatly, and because the charity of each of you toward one another is abundant
Certainly with these words they show the connection and narration of the first letter, since they show to them the progress of the same persons, in order that they might love the good things which they were more devotedly doing. In this act preachers are instructed that, while they know that their hearers have made progress, they must desire to show to them the same progress. To the extent that they give attention to their own progress, they should also love more firmly the good things which they do, and they should try to be imitators of the Thessalonians.