A Jerusalem Jew sometimes referred to in the New Testament as John Mark (Acts 12:12). He accompanied Paul and Barnabas, his cousin, to Antioch and traveled with them on their first missionary journey (Acts 12:25). At Perga, however, he left them and went home; no reason is given (Acts 13:13). This caused a split later between Paul and Barnabas when Paul refused to take Mark on their second journey. Barnabas was so incensed that he broke off his partnership with Paul and went on a voyage to Cyprus with Mark (Acts 15:36-39). Some years later, however, Paul and Mark were reunited and joined forces on another missionary trip. Mark was also closely associated with Peter, possible acting as his interpreter. Peter referred to him affectionately as "my son" (I Peter 5:13), probably considering him a protégé. Mark's greatest contribution was the authorship of the second Gospel. Estimates vary, but it was most probably written in the decade A.D. 60-70. Mark wrote in Greek, evidently for Christians, because he uses terms meaningless to nonbelievers. His Gospel is a blend of history and theology written in simple, forceful language.