Division among the brethren
What happens when an irresistible force meets an immovable object? What happens when two good men, two godly men, are equally convinced that quite opposite courses should be taken? In this case there was a very hot discussion. Barnabas presented all the positive reasons for including Mark in the new venture: he was young, he had promise, grace should prevail, he deserved a second chance. Paul presented all the reasons for not including Mark: he was unstable, he might fail again next time at an even more critical point, it was not fair to expose him to dangers (and dangers there would be) beyond his capacity to face, Mark had other talents, he had a way with words, let him be content serving the Lord within the framework of his talents and temperament.
The discussion grew heated. “And don’t you forget, Paul, how I took up your case when you needed a friend,” Barnabas might have said. “Come to think of it,” Paul might have angrily replied, “you dissembled right here at Antioch when Peter and the others refused to eat with the Gentiles. I’m not so sure about you any more, my brother.”
In the end, two angry men faced each other, sorry that it had come to such a pass but both quite inflexible over the central issue—John Mark. There was only one thing to do. Shake hands, and part company. How sad! How true to life.
John Phillips, Exploring Acts: An Expository Commentary, The John Phillips Commentary Series (Kregel Publications; WORDsearch Corp., 2009), Ac 15:39a.