John Calvin Commentary Acts 9:27

"But Barnabas took him, and brought him to the apostles, and declared unto them how he had seen the Lord in the way, and that he had spoken to him, and how at Damascus he had preached boldly in the name of Jesus." — Acts 9:27 (ASV)

When Barnabas had taken him. While the disciples fled so quickly from Paul, that was, perhaps, an instance of excessive fearfulness; and yet he speaks not of ordinary people, but of the apostles themselves. But he either lessens or lightens their fault, because they suspected him for good reasons, whom they had known and experienced to be such a deadly enemy.

And it was to be feared that they might rashly endanger themselves if they had shown themselves to be so easily persuaded.

Therefore, I think that they are not to be blamed for that fear which they felt for good reason, or that they even deserve to be accused for it. For if they had been called to give an account of their faith, they would have confronted not only Paul but also all the furies of hell, without fear.

From this we gather that not every fear is to be condemned, but only such fear as causes us to turn aside from our duty.

The narration which Luke adds may refer to Barnabas as well as to Paul. Yet I rather think that Paul declared to the apostles what had happened to him. And yet, the speech may well be applied to Barnabas, especially when mention is made of Paul’s boldness.