Charles Ellicott Commentary Acts 13:5

"And when they were at Salamis, they proclaimed the word of God in the synagogues of the Jews: and they had also John as their attendant." — Acts 13:5 (ASV)

When they were at Salamis.—The city was, as stated above, at the east end of Cyprus. The mention of “synagogues” implies a considerable Jewish population, and to these the Apostles, following the general rule announced in Acts 13:46, naturally, first, turned.

They had also John to their minister.—The noun so rendered is not that commonly used for the “deacons” or “ministers” of the Church, but implies instead personal assistance. It is probable, however, that he was employed in baptizing converts, and, where a church was founded, in preparing for the Supper of the Lord. Looking to the later work of Mark, it would hardly, perhaps, be too much to say that he was, more than any other disciple, the courier of the Apostolic Church.