John Calvin Commentary 1 Corinthians 2:4

"And my speech and my preaching were not in persuasive words of wisdom, but in demonstration of the Spirit and of power:" — 1 Corinthians 2:4 (ASV)

And my preaching was not in the persuasive words. By the persuasive words of man’s wisdom, he means that exquisite oratory which aims and strives by artifice rather than by truth, and also an appearance of refinement that allures the minds of men. It is not without good reason, too, that he ascribes persuasiveness (τό πιθάνον) to human wisdom.

For the word of the Lord constrains us by its majesty, as if by a violent impulse, to yield obedience to it. Human wisdom, on the other hand, has her allurements, by which she insinuates herself, and her blandishments, as it were, by which she may conciliate for herself the affections of her hearers.

With this he contrasts the demonstration of the Spirit and of power, which most interpreters consider restricted to miracles; but I take it in a more general sense, as meaning the hand of God powerfully exercised in every way through the instrumentality of the Apostle. He seems to have used Spirit and power by hypallage (καθ’ ὑπαλλαγήν) to denote spiritual power, or at least in order to show by signs and effects how the presence of the Spirit had shown itself in his ministry.

He appropriately, too, uses the term ἀποδείξεως (demonstration); for such is our dullness in contemplating the works of God, that when He makes use of inferior instruments, they serve as so many veils to hide His influence from us, so that we do not clearly perceive it. On the other hand, as in the advancement given to Paul’s ministry, there was no aid provided from the flesh or the world, and as the hand of God was, as it were, made bare (Isaiah 52:10), His influence was assuredly more apparent.