John Calvin Commentary 1 Thessalonians 2:4

"but even as we have been approved of God to be intrusted with the gospel, so we speak; not as pleasing men, but God who proveth our hearts." — 1 Thessalonians 2:4 (ASV)

As we have been approved. He goes even a step higher, for he appeals to God as the Author of his apostleship, and he reasons in this way: “God, when he assigned me this office, bore witness to me as a faithful servant; there is no reason, therefore, why men should have doubts about my fidelity, which they know to have been approved of by God.”

Paul, however, does not glory in having been approved of, as though he were so by his own merit. For he does not dispute here about what he had by nature, nor does he place his own power in collision with the grace of God, but simply says that the Gospel had been committed to him as a faithful and approved servant. Now, God approves of those whom he has formed for himself according to his own pleasure.

Not as pleasing men. What is meant by pleasing men has been explained in the Epistle to the Galatians (Galatians 1:10), and this passage also shows it admirably. For Paul contrasts pleasing men, and pleasing God, as things that are opposed to each other. Further, when he says, God, who trieth our hearts, he intimates that those who endeavor to obtain the favor of men are not influenced by an upright conscience and do nothing from the heart.

Therefore, let us understand that true ministers of the gospel ought to make it their aim to devote their endeavors to God, and to do it from the heart, not from any outward regard for the world, but because conscience tells them that it is right and proper. This will ensure that they will not make it their aim to please men; that is, that they will not act under the influence of ambition, seeking the favor of men.