John Mark
Mark 6:12ESV·traditional attribution

So they went out and proclaimed that people should repent.

John Calvin Reformed @genevareformer

Mark 6:12. And they departed, and preached. Matthew silently passes over what the Apostles did. Mark and Luke relate that they proceeded to execute the commission which they had received; and from their statements it appears more clearly, that the office which Christ at that time bestowed upon them, as I have formerly mentioned, was temporary, and indeed lasted but a few days.

Matthew Henry Presbyterian @wholebiblehenry

Here is, I. The commission given to the twelve apostles, to preach and work miracles; it is the same which we had more largely, Mt. 10. Mark doth not name them here, as Matthew doth, because he had named them before, when they were first called into fellowship with him, Mar 3:16-19.

Commenting on Mark 6:7-13

John Gill Reformed Baptist @doctorgill

And they went out,.... From that part of the country where they then were, some one way, and some another, two by two, with these instructions, and according to these directions; in order to preach the word, and work miracles, in the several parts where they were sent: and preached that men should repent; both of the evil practices which they were guilty of, and...