After some days Paul said to Barnabas, "Come, let us return and visit the believers in every city where we proclaimed the word of the Lord and see how they are doing."
References for Acts 15:36
Barnabas wanted to take with them John called Mark.
But Paul decided not to take with them one who had deserted them in Pamphylia and had not accompanied them in the work.
The disagreement became so sharp that they parted company; Barnabas took Mark with him and sailed away to Cyprus.