Albert Barnes on Acts 13:5

And when they were at Salamis. This was the principal city and seaport of Cyprus. It was situated on the south-east part of the island, and was afterwards called Constantia.

In the synagogues of the Jews. Jews were living in all the countries adjacent to Judea; and in those countries they had synagogues. The apostles uniformly preached first to them.

And they had also John to their minister. John Mark, Acts 12:12. He was their attendant; he was with them as a companion, yet not pretending to be equal to them in office. They had been specifically designated to this work. He was with them as their friend and travelling companion; perhaps also employed in making the needful arrangements for their comfort, and for the supply of their wants in their travels.

(+) "minister" "For their attendant"