Barnabas (Saint Barnabus in Catholic and Orthodox traditions) was a Jew from Cyprus (Acts 4:36) and an important member of the Church of Jerusalem early in its founding history after the death of Jesus. His role in the early church is discussed in the Bible in the Book of Acts.
It was Barnabas who first stood up for Paul to allow him to be fully accepted into the Jerusalem Church since even the Disciples were afraid of him due to his past of persecuting Christians. (Acts 9:27) Barnabas was sent by the Jerusalem Church to Antioch, where a "great number of people believed and turned to the Lord" from the preaching of other Christians who were scattered due to the persecution of the church in Jerusalem. Barnabas saw the great acts being done and encouraged them to "remain true to the Lord with all of their hearts" (Acts 11:22-23) He went and got Paul to join him. (Acts 11:25) Barnabus and Paul carried the love offering back to the Jerusalem church when a famine spread over the Roman world in 43 A.D. (Acts 11:29-30)
Barnabas and Paul went on a missionary journey together from 46 to 48 A.D. They took with them John Mark, the author of the Gospel of Mark. (Acts 12:25) During this journey, Paul rose to prominence over Barnabas. When they prepared for a second missionary journey in 50 A.D., Barnabas wished to have John Mark accompany them again. Paul refused since John Mark had left them on the first journey. Unable to resolve their difference, Paul and Barnabas went their separate ways, with Barnabas and John Mark going to Cyprus to preach the Good News there.