But Paul thought it best not to take him, because he had deserted them in Pamphylia and had not accompanied them in the work.
Paul thinks it best not to take Mark because he had deserted them in Pamphylia and had not continued with them in the work.
It states Paul's reason for refusal.
36Some time later Paul said to Barnabas, “Let us go back and visit the brothers in every town where we proclaimed the word of the Lord, to see how they are doing.” 37Barnabas wanted to take John, also called Mark. 38But Paul thought it best not to take him, because he had deserted them in Pamphylia and had not accompanied them in the work. 39Their disagreement was so sharp that they parted company. Barnabas took Mark and sailed for Cyprus, 40but Paul chose Silas and left, commended by the brothers to the grace of the Lord. 41And he traveled through Syria and Cilicia, strengthening the churches.