As we previously pointed our in verses1-7, Paul had a great love for the Thessalonians which led to his ministry to them. The though continues in these verses, as he declares his affection, and his willingness even to die in his efforts to share with them the “gospel of God.”
The Thessalonians were well aware of Paul’s efforts, as he had labored diligently among them. Further, his secular worked was a testament to his love, so that he would not be a financial burden to the brethren there. (Though note, such support was certainly scripturally defensible, cf. 1 Timothy 5:18).
But Paul, in every way wanted only to benefit his brethren. Thus he always acted in a way to protect his reputation, that his work of ministry would not be hindered. He acted, “devoutly and justly and blamelessly” among them.
Paul’s concern was not for himself — only for them! His hope for them was a worthy walk, and an eternal reward.