What was the source of the disagreement between Paul and Barnabas over John Mark?

John Mark was a young man, known, in the Bible, by the name Mark. He traveled with Barnabas and Paul, who worked as an evangelical team, preaching the Gospel of Jesus Christ.

They faced many hardships as they ministered. At a place called Pamphylia, John Mark didn't want to go on with the two men. Later, Barnabas wanted to include the young man in a missionary journey. Paul said no. He was against it because John Mark, Paul had decided, had deserted the mission before.

This refusal to allow John Mark to travel with them caused some hard feelings between Paul and Barnabas. They decided to go their separate ways to carry out Christ's work. Barnabas took John Mark with him.

Later in his life, Paul embraced Mark. He said Mark was profitable (very useful) in helping him carry out the Lord's work.