Paul and Barnabas
Here it appears either Paul or Barnabas went too far. It must have been a violent disagreement to separate two associates who were so closely united. Indeed, the text indicates as much.
Such examples are written for our consolation: for it is a great comfort to us to hear that great saints, who have the Spirit of God, also struggle. Those who say that saints do not sin would deprive us of this comfort. Samson, David, and many other celebrated men full of the Holy Spirit fell into grievous sins. Job and Jeremiah cursed the day of their birth; Elijah and Jonah were weary of life and desired death. No one has ever fallen so grievously that he may not rise again. Conversely, no one stands so firmly that he may not fall. If Peter (and Paul and Barnabas) fell, I too may fall. If they rose again, I too may rise again.