But Barnabas - See the notes on Acts 4:36. Barnabas was of Cyprus, not far from Tarsus, and it is not improbable that he had been before acquainted with Saul.
To the apostles - To Peter and James, Galatians 1:18-19. Probably the other apostles were at that time absent from Jerusalem.
And declared unto them ... - It may seem remarkable that the apostles at Jerusalem had not before heard of the conversion of Saul. The following considerations may serve in some degree to explain this:
(1) It is certain that contact between different countries was then much more difficult than it is now. There were no posts; no public conveyances; no mails; no telegraphs; nothing that corresponded with our modes of contact between one part of the world and another.
(2) There was at this time a state of animosity amounting to hostility subsisting between Herod and Aretas. Herod the tetrarch had married the daughter of Aretas, king of Arabia, and had put her away (Josephus, Antiq., book 18, chapter 5, section 1, 2). The result of this was a long misunderstanding between them, and a war; and the effects of that war might have been to interrupt the communication very much throughout all that country.
(3) Though the Jews at Jerusalem might have heard of the conversion of Saul, yet it was for their interest to keep it a secret, and not to mention it to Christians. But,
(4) Though the Christians who were there had heard of it, yet it is probable that they were not fully informed on the subject; that they had not had all the evidence of his conversion which they desired; and that they looked with suspicion on him. It was therefore proper that they should have a full statement of the evidence of his conversion; and this was made by Barnabas.