John Chrysostom

"But Barnabas" - "Son of Consolation" is his appellation, whence also he makes himself easy of access to the man: for "he was a kind man" (ch. xi. 24), exceedingly, and this is proved both by the present instance, and in the affair of John (Mark) - "having taken him, brought him to the Apostles, and related to them how he had seen the Lord in the way." It is likely that at Damascus also he had heard all about him: whence he was not afraid but the others were, for he was a man whose glance inspired fear.

Homily on Acts 21 ↗

Theophylact of Ohrid

That Barnabas was a gentle and condescending man is evident both from this and from what was done by him after this. Perhaps he had known Paul even before, being his friend. To which apostles did he bring Paul? Perhaps to Peter and James, of whom Paul himself also speaks in the Epistle to the Galatians, saying that he knew them. Pay attention to Paul: he does not go to the apostles, as a man who thinks humbly of himself, but goes to the disciples, as if he too were only a disciple. …

Commentary on Acts ↗

Bede

But Barnabas took him and brought him to the apostles, and narrated to them how he had seen the Lord on the way, etc. When these things were done, and to which apostles Barnabas brought Paul, Paul himself shows, writing to the Galatians: But when it pleased Him who separated me from my mother's womb, and called me by His grace, to reveal His Son in me, and so forth, until he says: Then after three years I went up to Jerusalem to see Peter, and stayed with him fifteen days. …

Retractions on Acts ↗