Paul and Barnabas Agree To Separate (15:36-39).
The ministry of Paul and Barnabas now continued in Syrian Antioch for some time. But the question would eventually necessarily arise as to the wellbeing of the churches that they had been used by God in establishing. Thus Paul one day suggested to Barnabas that it was time that they returned to those cities where they had established churches in order to minister to them and see how they fared. And this appears to have been mutually agreed. The date would be around 49 AD.
However, in the event, because of disagreement over John Mark they separated their ministries and by mutual agreement each took responsibility for one section of the work that they had accomplished together. There is no reason why we should not see this as having been accomplished fairly amicably. Christians can disagree on such things without fighting. This would in fact result in a wider work being done than would otherwise have been possible. As in the case of persecution previously, God used man's weaknesses in order to advance His purposes. He was sovereign in all that happened.