John Calvin Commentary Acts 28:25

"And when they agreed not among themselves, they departed after that Paul had spoken one word, Well spake the Holy Spirit through Isaiah the prophet unto your fathers," — Acts 28:25 (ASV)

And when they could not—The malice and stubbornness of the unfaithful is the cause of this: that Christ, who is our peace and the only bond of holy unity, becomes an occasion of dissension and causes those who were friends before to quarrel.

For consider, when the Jews come together to hear Paul, they all think the same thing and speak the same thing; they all profess that they embrace the law of Moses. As soon as they hear the doctrine of reconciliation, dissension arises among them, so that they are divided.

And yet, despite all this, we must not think that the preaching of the gospel is the cause of discord. Rather, it is that hidden displeasure, which lurked before in their malicious minds, that then breaks out. Just as the brightness of the sun does not color things differently than they were, but plainly shows the difference that was unseen as long as it was dark.

Therefore, since God illuminates His elect in a special way, and faith is not common to all people, let us remember that it is inevitable that, as soon as Christ is made known, there will be a division among humanity. But then let us call to mind what Simeon foretold about Him: he shall be a sign which shall be spoken against, that the thoughts of many hearts may be disclosed (Luke 2:34, 35), and that unbelief which strives against God is the mother of dissension.

After that Paul.—At first, he sought to win them over meekly and gently. Now, as soon as he perceives their obstinacy, he denounces them sharply and severely proclaims the judgment of God.

For the rebellious must be handled this way, as their pride cannot be tamed with plain doctrine. We must follow the same method: we must gently guide those who are teachable and gentle, but we must summon the stubborn to God’s judgment seat.

When Paul introduces the Holy Spirit speaking, rather than the prophet, it adds to the credibility of the oracle. For since God requires that He alone be heard, doctrine cannot otherwise have authority unless we know that it proceeded from Him and did not originate from a human mind.

Furthermore, he thereby declares that it is not only the stubbornness of one age that is noted there, but that the oracle of the Spirit extends to future times.