Acts 13:5

And when they were at Salamis, they preached the word of God in the synagogues of the Jews: and they had also John to their minister.

And when they were at Salamis - the Grecian capital of the island, situated on its eastern side, and not many hours' sail from Seleucia,

They preached the word of God in the synagogues of the Jews. At this busy mercantile port immense numbers of Jews were settled; which accounts for its being here said that they had more than one synagogue, in which Barnabas and Saul preached, while other cities had one only. Zeller (of the Tubingen school of critics) makes a miserable attack on the authenticity of this book, grounded on their being sent forth to preach to the Gentiles while yet they are represented as beginning their mission by doing just the reverse-preaching to the Jews and neglecting the Gentiles. But who knows not that the apostles in this matter acted throughout on a principle? - "To the Jew first, and also to the Greek" (Romans 1:16). See the notes at Acts 13:46-44.

And they had also John (John Mark, Acts 12:25 ) to their minister, [ hupeereteen (G5257)] - or, 'as their officer.' With regard to the official so called in the Jewish synagogue, see the note at Luke 4:20. But Mark, no doubt, was their 'assistant' in a more general sense, performing all the subordinate services of the mission. With what fruit they now preached is not said; and as success is always noticed in this book, its silence here is ominous.