Ambrose of Milan
Catena Aurea · Lukasevangelium 6
And it came to pass in those days, that he went out into a mountain to pray, and continued all night in prayer to God. And when it was day, he called unto him his disciples: and of them he chose twelve, whom also he named apostles; Simon, (whom he also named Peter,) and Andrew his brother, James and John, Philip and Bartholomew, Matthew and Thomas, James the son of Alphæus, and Simon called Zelotes, And Judas the brother of James, and Judas Iscariot, which also was the traitor.
Every where also He prays alone, for human wishes comprehend not the wisdom of God; and no one can be a partaker of the secrets of Christ. But not every one who prays ascends a mountain, he only who prays advancing from earthly things to higher, who is not anxious for the riches or honours of the world. All whose minds are raised above the world ascend the mountain. In the Gospel therefore you will find, that the disciples alone ascend the mountain with the Lord. But thou, O Christian, hast now the character given, the form prescribed which thou shouldest imitate; as it follows, And he continued all night in prayer to God. For what oughtest thou to do for thy salvation, when Christ continues all night in prayer for thee?