Theophylact of Ohrid, on Acts 12:12

“And considering, he came to the house of Mary the mother of John, who was surnamed Mark, where many were gathered together and praying.”

“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.”

Imported from an open dataset — not yet checked against the printed edition.