John Calvin Commentary Acts 18:4

"And he reasoned in the synagogue every sabbath, and persuaded Jews and Greeks." — Acts 18:4 (ASV)

He disputed in the synagogue. It is a wonder how the statement that Paul introduced the name of Christ crept into the Latin books, unless it was because some reader wished to complete the general sentence. For Luke records two things in this passage: namely, that Paul disputed among the Jews, and secondly, that he began to profess Christ more plainly after Silas and Timothy had come.

And though it is likely that he began to speak of Christ right from the start, because he could not omit the principal point of the heavenly doctrine, yet that does not prevent him from using some other manner of disputation. Therefore, I take [πειθειν]—that is, to persuade—to mean to induce by little and little. For, in my judgment, Luke signifies that because the Jews handled the law coldly and foolishly, Paul spoke of the corrupt and wicked nature of man, of the necessity of grace from the promised Redeemer, and of the means to obtain salvation, in order to awaken them; for this is a fitting and brief preparation for Christ.

Again, when he says that he was forced in spirit to teach that Jesus was Christ, his meaning is that he was compelled with greater vehemence to discourse on and speak of Christ freely and openly. So we see that Paul did not reveal all things at one time, but he tempered his doctrine as the occasion required.

And because similar moderation is profitable today, it is advisable for faithful teachers to consider wisely where to begin, lest a preposterous and confused order hinder the progress of doctrine. Furthermore, though there was enough fervency in Paul, yet it is not unfitting that he was made more courageous by some new help—not that he was encouraged by shame or by the hope he placed in his companions, but because he considered that this help was sent to him, as it were, from heaven.

But this "forcing in the spirit" is not to be understood as a violent or external impulse (as they say), like those who were called Phoebades and frantic men used to be carried away with devilish madness. Instead, more fervency was added to the usual inspiration of the Spirit that was in Paul, so that he was moved with new power from God; and yet, of his own accord, he still followed the Spirit as his guide.

When Paul testified that Jesus is Christ, I explain it this way: after he had thoroughly taught the Jews concerning the office of the Redeemer, he declared by testimonies from Scripture that this is He for whom they were to hope. This was because all those things that the Law and the Prophets attribute to Christ are fulfilled in Him. Therefore, Paul did not simply affirm this, but using solemn testimony, he proved Jesus, the Son of Mary, to be that Christ who was to be the Mediator between God and men, in order to restore the world from destruction to life.