Memorial; June 11
St. Barnabas was a very early member of the Church. Born a Levite on Cyprus, he spent much time in Jerusalem. According to most accounts, he converted during the Pentecost and is mentioned in Acts for selling his property and giving the proceeds to the church (Acts 4:34-37).
Barnabas introduced Paul to the Apostles, who were wary and slow to believe his conversion. Much of Barnabas’s ministry after this involves Paul. He convinced Paul to start his journeys in Antioch, and accompanied on many of his voyages. His desire to bring St. Mark (the Gospel writer) along with them on one of the journeys caused a temporary rift with Paul. Barnabas was present at the Council of Jerusalem, and sided with Paul on the circumcision debate.
After his journeys, not much is written about Barnabas. He was one of the most highly esteemed men of the Church outside of the 12 Apostles. Many writings are attributed to him: Tertullian attributes the Letter to the Hebrews, Photius claims Barnabas, not Luke, wrote Acts of the Apostles and many attribute the Epistle of Barnabas to him, but these claims are doubted.
Further reading:
The Catholic Encyclopedia, http://www.newadvent.org/cathen/02300a.htm
Wikipedia, http://en.wikipedia.org/wiki/Barnabas