Theophylact of Ohrid
Catena Aurea · Markusevangelium 3
And he goeth up into a mountain, and calleth unto him whom he would: and they came unto him. And he ordained twelve, that they should be with him, and that he might send them forth to preach, And to have power to heal sicknesses, and to cast out devils: And Simon he surnamed Peter; And James the son of Zebedee, and John the brother of James; and he surnamed them Boanerges, which is, The sons of thunder: And Andrew, and Philip, and Bartholomew, and Matthew, and Thomas, and James the son of Alphæus, and Thaddæus, and Simon the Canaanite, And Judas Iscariot, which also betrayed him.
Luke, however, says that He went up to pray, for after the shewing forth of miracles He prays, teaching us that we should give thanks, when we obtain any thing good, and refer it to Divine grace.