John Calvin Commentary Acts 18:9

"And the Lord said unto Paul in the night by a vision, Be not afraid, but speak and hold not thy peace:" — Acts 18:9 (ASV)

And the Lord said. Though the fruit of Paul’s doctrine (because he daily won some to Christ) might have encouraged him to go forward, yet the heavenly oracle was added for his further confirmation. From this we gather that great combats were set before him, and that he was severely tossed in various ways.

For the Lord never, without cause, poured out His oracles; neither was it an ordinary thing for Paul to have visions, but the Lord used this kind of remedy when necessity required it. And this itself shows that a great weight of business lay upon the holy man, under which he might not only sweat but almost faint, unless he had been restored and refreshed with some new help.

And it is not without cause that he says that his coming was base and contemptible, and that he was present there in fear and trembling (1 Corinthians 2:3). For my own part, I think that the wonderful power of the Spirit, with which Paul was endowed before, was helped by the oracle. Furthermore, since the Scripture distinguishes visions from dreams, as it appears from the twelfth chapter of the book of Numbers (Numbers 12:6), Luke means by this word vision, that when Paul was in a trance he saw a certain shape or form by which he knew that God was present with him. Assuredly, it is not to be doubted that God appeared by some sign.

Fear not. This exhortation shows that Paul had cause for fear given to him, for it would have been superfluous to correct fear, or to tell him not to fear when all was well and quiet, and especially in a man so willing and ready.

Furthermore, when the Lord (so that His servant might do his duty faithfully and resolutely) begins by restraining fear, from this we gather that nothing is more contrary to the pure and free preaching of the gospel than the constraints of a faint heart. And surely experience shows that none are faithful and courageous ministers of the word who are hindered by this fault; and that only those are rightly prepared and equipped to teach to whom it is granted, with boldness and courage of heart, to overcome every kind of danger.

In this regard, he writes to Timothy that the spirit of fear is not given to the preachers of the gospel, but of power, and love, and sobriety (2 Timothy 1:7). Therefore, we must note the connection of words, Fear not, but speak, which is the same as if he had said, Do not let fear prevent you from speaking.

And because fear not only makes us entirely speechless, but also so binds us that we cannot purely and freely speak what is needful, Christ touched upon both aspects briefly. Speak, (He said) and hold not your peace; that is, do not speak with half your mouth, as the common proverb says.

But in these words a common rule is prescribed to the ministers of the word of God: that they expound and set forth plainly, and without embellishment or concealment, whatever the Lord wishes to be made known to His Church. Indeed, they should keep back nothing that may contribute to the edification or growth of God’s Church.