Catholics celebrate the memory of St. Barnabas on June 11. The apostle and missionary was among Christ's earliest followers and was responsible for welcoming St. Paul into the Church. Though not one of the 12 apostles chosen by the Lord, Jesus, he is traditionally regarded as one of the 72 disciples of Christ and most respected man in the first century Church after the Apostles themselves.

St. Barnabas was born to wealthy Jewish parents on the Greek-speaking island of Cyprus, probably around the time of Christ's own birth. Traditional accounts hold that his parents sent him to study in Jerusalem, where he studied at the school of Gamaliel (who also taught St. Paul). Later on, when Christ's public ministry began, Barnabas may have been among those who heard him preach in person. At some point, either during Christ's ministry or after his death and resurrection, Barnabas decided to commit himself in the most radical way to the teachings he had received. He sold the large estate he had inherited, contributed the proceeds entirely to the Church, and joined Christ's other apostles in holding all of their possessions in common. Saul of Tarsus, the future St. Paul, approached Barnabas after the miraculous events surrounding his conversion, and was first introduced to St. Peter through him. About five years later, Barnabas and Paul spent a year in Antioch, building up the Church community whose members were the first to go by the name of “Christians.” Both Paul and Barnabas received a calling from God to become the “Apostles of the Gentiles,” although the title is more often associated with St. Paul. The reference to the “laying-on of hands” in Acts, chapter 13, suggests that Paul and Barnabas may have been consecrated as bishops on this occasion.

Barnabas and Paul left Antioch along with Barnabas' cousin John Mark, who would later compose the most concise account of Christ's life and be canonized as St. Mark. The group's first forays into the pagan world met with some success, but Mark became discouraged and returned to Jerusalem. The question of Mark's dedication to the mission would arise again later, and cause a significant personal disagreement between Paul and Barnabas. For many years prior to this, however, the two apostles traveled and preached among the Gentiles, suffering persecution and hardships for the sake of establishing Christianity among those of a non-Jewish background. The remarkable success of Barnabas and Paul led to one of the earliest controversies in Church history, regarding the question of whether Christian converts would have to observe Jewish rites. During the landmark Council of Jerusalem, recorded in the book of Acts, the assembled apostles confirmed St. Peter's earlier proclamation that the laws of the Old Testament would not be mandatory for Christians.

Barnabas and Paul finally separated in their ministries, while remaining apostles of the one Catholic Church, over Paul's insistence that Mark not travel with them again. In death, however, the “Apostles to the Gentiles” were reunited. Mark is said to have buried Barnabas after he was killed by a mob in Cyprus around the year 62. St. Paul and St. Mark were, in turn, reconciled before St. Paul's martyrdom five years later. He is said to have been stoned to death in Salamis in the year 61. St. Luke described Barnabas as 'a good man, full of the Holy Spirit and of faith' (Acts 6:24), and he was known for his exceptional kindliness and personal sanctity, and his openness to pagans.