Acts 12:12

“This also the presbyter [John] said: Mark, having become the interpreter of Peter, wrote down accurately, though not in order, whatsoever he remembered of the things said or done by Christ. For he neither heard the Lord nor followed him, but afterward, as I said, he followed Peter, who adapted his teaching to the needs of his hearers, but with no intention of giving a connected account of the Lord's discourses, so that Mark committed no error while he thus wrote some things as he remembered them. For he was careful of one thing, not to omit any of the things which he had heard, and not to state any of them falsely.”

“And when he had considered, it says: viz. where he was, or, that he must not without more ado depart but requite his Benefactor: he came to the house of Mary the mother of John. Who is this John? Probably he that was always with them: for this is why he adds his distinctive name, "whose surname was Mark." But observe, "praying" in the night, how much they got by it: what a good thing affliction is; how wakeful it made them! Do you see how great the gain resulting from the death of Stephen? do you see how great the benefit accruing from this imprisonment? For it is not by taking vengeance upon those who wronged them that God shows the greatness of the Gospel: but in the wrong-doers themselves, without any harm happening to those, he shows what a mighty thing the afflictions in themselves are, that we may not seek in any wise deliverance from them, nor the avenging of our wrongs.”

“And when he had considered, he came to the house of Mary. Then let us not hide God's marvels, but for our own good let us study to display these abroad for the edifying of the others. For as he deserves to be admired for choosing to be put into bonds, so is he worthy of more admiration, that he withdrew not until he had reported all to his friends.”

“Upon reflection, he saw that he should not simply continue on his way, but rather give thanks to the Benefactor. This John was perhaps not the one who constantly remained with the apostles. That is why the writer added his distinguishing name, since he said: "who was called Mark." Perhaps this is Mark the Evangelist, through whom, they say, Peter transmitted his Gospel, since the Gospel of Mark is said to be Peter's Gospel. This supposition is justified by the fact that Peter and the other apostles spent a considerable amount of time at his house.”

“"who was called Mark." In order to show that he does not mean John, who was always with them, he names his mother and gives his distinguishing nickname, for he says, "who was called Mark." This man was the same who wrote the Gospel according to Mark, the nephew of Barnabas, concerning whom Paul writes to Timothy: "Take Mark and bring him with you when you come, for he is useful to me for ministry." (2 Tim. 4:11)”