The summary statement of Peter's report is rich in doctrinal meaning, "God granted to the gentiles repentance unto life." On the one hand it looked like a unique gift of the Holy Spirit, but it established the lowest common denominator -- they came to faith the same way anyone does. This was sufficient authentication to make all Jerusalem be quiet and praise God.
Barnabas played another significant role. He encouraged then to purpose to remain in the Lord. He did that because he was a good man, full of the Holy Spirit and faith. That's what faithful, Spirit-filled, good men do! That's what I want to be and do.
This is the first step in the decentralization of the church. The Antioch church sent a gift back to Jerusalem! Wow! God made sure it happened with supernatural prophecy. Interesting!