1 Corinthians 9:6

Barnabas] was like St. Paul, an Apostle (Acts 14:14), and like him, but unlike the rest, he maintained himself by his own labour. They may have jointly adopted this course on their missionary journeys (Acts 13:14). We see that Barnabas was known to the Corinthians, and still working as a missionary. For St. Paul's self-support see on 1 Corinthians 4:12.

7-14. Proof of this right. This right is proved (1 Corinthians 9:7) from the analogy of soldiers, husbandmen, shepherds; (1 Corinthians 9:8) from the direction in the Law that the ox should not be muzzled (1 Corinthians 9:11) on grounds of common fairness and gratitude; (1 Corinthians 9:13) from the example of the Jewish priesthood.