John Calvin Commentary Acts 16:9

"And a vision appeared to Paul in the night: There was a man of Macedonia standing, beseeching him, and saying, Come over into Macedonia, and help us." — Acts 16:9 (ASV)

A vision by night. The Lord did not want Paul to stay any longer in Asia because He intended to draw him into Macedonia. And Luke expresses the manner of this drawing: that a man of Macedonia appeared to him by night. Here we must note that the Lord did not always observe the same manner of revelation, because different kinds are more suitable for confirmation. And it is not said that this vision came in a dream, but only during the night. For there are certain night visions which people see when they are awake.

Help us. This speech sets forth the ministry committed to Paul. For, since the gospel is the power of God to salvation (Romans 1:16), those who are the ministers of God are said to help those who perish, so that, having delivered them from death, they may bring them to the inheritance of eternal life.

And this should be a significant encouragement for godly teachers to stir up their fervent study and desire, when they hear that they call back wretched souls from destruction and help those who would otherwise perish, so that they may be saved.

Again, all people to whom the gospel is brought are taught to reverently embrace its ministers as deliverers, unless they maliciously reject the grace of God.

And yet, this commendation and title is not transferred to people in such a way that God is robbed of even the best part of His praise. For although He gives salvation through His ministers, yet He is its only author, as if He reached out His hands to help.