How ye turned to God from idols - This could not be spoken either of the Jews or of the devout persons, but of the heathen Greeks, and of such it appears that the majority of the Church was formed. See what is said on this subject in the preface to this epistle.
To serve the living and true God - The living God; in opposition to the idols, which were either inanimate stocks or stones, or the representations of dead men.
The true God - In opposition to the whole system of idolatry, which was false in the objects of its adoration, false in its pretensions, false in its promises, and false in all its prospects.
For they themselves - They who have visited you, and they whom you have sent out; all persons testify of your piety. The apostle seems to refer to all whom he had met or had heard of “in all places,” who said anything about the Thessalonians They were unanimous in bearing testimony to their fidelity and piety.
Show of us what manner of entering in we had unto you - The testimony which they bear of you is, in fact, testimony of the manner in which we preached the gospel, and demeaned ourselves when we were with you. It shows that we were intent on our Master‘s work, and that we were not actuated by selfish or sinister motives The argument is, that such effects could not have been produced among them if Paul, Silas, and their fellow laborers had been impostors. Their sound conversion to God; their change from idolatry to the true religion, and the zeal which had been the result of their conversion, was an argument to which Paul and his fellow-laborers might appeal in proof of their sincerity and their being sent from God. Paul often makes a similar appeal; compare notes on 2 Corinthians 3:2-3. It is certain that many of the Jews in Thessalonica, when Paul and his fellow-laborers were there, regarded them as impostors Acts 17:6, Acts 17:8, and there is every reason to suppose that after they left the city, they would endeavor to keep up this impression among the people. To meet this, Paul now says that their own undoubted conversion to a life of holiness and zeal under their ministry, was an unanswerable argument that this was not so. How could impostors and deceivers have been the means of producing such effects?
And how ye turned to God from idols - That is, under our preaching. This proves that the church was to a considerable extent composed of those who were converted from idolatry under the preaching of Paul; compare Intro. 4. The meaning here is, that they who came from them, or they who had visited them, bore abundant testimony to the fact that they had turned from idols to the worship of the true God; compare notes 1 Corinthians 12:2; Galatians 1:8.
To serve the living and true God - He is called the “living God” in opposition to idols - who are represented as dead, dumb, deaf, and blind; compare Psalm 135:15-17; notes, Isaiah 44:10-17; Matthew 16:16; John 5:26; Acts 14:15.