12 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.
[AD 220] Tertullian on Luke 6:12
Surely to Sion He brings good tidings, and to Jerusalem peace and all blessings; He goes up into a mountain, and there spends a night in prayer, and He is indeed heard by the Father.

[AD 258] Cyprian on Luke 6:12
Let us urgently pray and groan with continual petitions. For know, beloved brethren, that I was not long ago reproached with this also in a vision, that we were sleepy in our prayers, and did not pray with watchfulness; and undoubtedly God, who "rebukes whom He loves, when He rebukes, rebukes that He may amend, amends that He may preserve. Let us therefore strike off and break away from the bonds of sleep, and pray with urgency and watchfulness, as the Apostle Paul bids us, saying, "Continue in prayer, and watch in the same." For the apostles also ceased not to pray day and night; and the Lord also Himself, the teacher of our discipline, and the way of our example, frequently and watch-fully prayed, as we read in the Gospel: "He went out into a mountain to pray, and continued all night in prayer to God." And assuredly what He prayed for, He prayed for on our behalf, since He was not a sinner, but bore the sins of others. But He so prayed for us, that in another place we read, "And the Lord said to Peter, Behold, Satan has desired to sift you as wheat: but I have prayed for thee, that thy faith fail not." But if for us and for our sins He both laboured and watched and prayed, how much more ought we to be instant in prayers; and, first of all, to pray and to entreat the Lord Himself, and then through Him, to make satisfaction to God the Father! We have an advocate and an intercessor for our sins, Jesus Christ the Lord and our God, if only we repent of our sins past, and confess and acknowledge our sins, whereby we now offend the Lord, and for the time to come engage to walk in His ways, and to fear His commandments. The Father corrects and protects us, if we still stand fast in the faith both in afflictions and perplexities, that is to say, cling closely to His Christ; as it is written, "Who shall separate us from the love of Christ? Shall tribulation, or distress, or persecution, or famine or nakedness, or peril, or sword? None of these things can separate believers, nothing can tear away those who are clinging to His body and blood. Persecution of that kind is an examination and searching out of the heart. God wills us to be sifted and proved, as He has always proved His people; and yet in His trials help has never at any time been wanting to believers.

[AD 339] Eusebius of Caesarea on Luke 6:12-16
The two next are James and John, as it follows, James and John, both indeed sons of Zebedee, who were also fishermen. After them he mentions Philip and Bartholomew. John says Philip was of Bethsaida, of the city of Andrew and Peter. Bartholomew was a simple man, devoid of all worldly knowledge and guile. But Matthew was called from those who used to collect taxes; concerning whom he adds Matthew and Thomas.

[AD 397] Ambrose of Milan on Luke 6:12
So the Lord prays, not to entreat for himself but to intercede for me. Although the Father placed all things in the power of his Son, yet the Son, in order to fulfill the form of a man, thinks that the Father must be entreated for us, because he is our Advocate.… If he is an Advocate, he must intercede on account of my sins.…It says, “He passed the whole night in prayer.” A model is given to you. A form is prescribed which you must imitate.… Unless I am mistaken, it is nowhere found that he prayed with the apostles. Everywhere he entreats alone, for human prayers do not grasp the counsels of God, nor can anyone share with Christ in the inward mysteries.

[AD 397] Ambrose of Milan on Luke 6:12-16
You have heard then the words of Him who says, Stretch forth thy hand. That is a frequent and common cure, and thou that thinkest thy hand is whole, beware lest it be contracted by avarice or sacrilege. Stretch it forth oftener to help thy neighbour, to protect the widow, to save from injury him whom you see the victim of unjust attack; stretch it forth to the poor man who beseeches thee; stretch it forth to the Lord, to ask pardon of thy sins; as the hand is stretched forth so is it healed. (1 Kings 13:5, 6.)

Let not thy ears be open to deceit, that thou shouldest think that the Son of God prays from want of strength, that He may obtain what He could not perform; for being Himself the Author of power, the Master of obedience, He leads us by His own example to the precepts of virtue.

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?

But what does it become thee to do when thou wouldest commence any work of piety, when Christ, about to send out His disciples, first prayed? for it follows, And when it was day, he called his disciples, &c. whom truly He destined to be the means of spreading the salvation of man through the world. Turn thy eyes also to the heavenly council. Not the wise men, not the rich, not the noble, but He chose to send out fishermen and publicans, that they might not seem to turn men to their grace by riches or by the influence of power and rank, and that the force of truth, not the graces of oratory, might prevail.

[AD 407] John Chrysostom on Luke 6:12-16
(Hom. ad Pop. Ant. 42. et in Act. c. 16. Ed. Lat.) Rise then thou also at night time. The soul is then purer, the very darkness and great silence are in themselves enough to lead us to sorrow for our sins. But if thou lookest upon the heaven itself studded with stars as with unnumbered eyes, if thou thinkest that they who wanton and do unjustly in day time are then nothing different from the dead, thou wilt loathe all human undertakings. All these things serve to raise the mind. Vain-glory then disquiets not, no tumult of passion has the mastery; fire does not so destroy the rust of iron as nightly prayer the blight of sin. He whom the heat of the sun has fevered by day is refreshed by the dew; nightly tears are better than any dew, and are proof against desire and fear. But if a man is not cherished by the dew we speak of, he withers in the day. Wherefore although thou prayest not much at night, pray once with watching, and it is enough; show that the night belongs not only to the body, but to the soul.

[AD 430] Augustine of Hippo on Luke 6:12-16
(de Con. Ev. lib. ii. c. 30.) With respect to the name of Judas the brother of James, Luke seems to differ from Matthew, who calls him Thaddæus. But what prevented a man from being called by two or three names? Judas the traitor is chosen, not unwittingly but knowingly, for Christ had indeed taken to Himself the weakness of man, and therefore refused not even this share of human infirmity. He was willing to be betrayed by His own Apostle, that thou when betrayed by thy friend mayest bear calmly thy mistaken judgment, thy kindness thrown away.

[AD 444] Cyril of Alexandria on Luke 6:12-16
Let us examine then in the actions which Jesus did, how He teaches us to be instant in prayer to God, going apart by ourselves, and in secret, no one seeing us; putting aside also our worldly cares, that the mind may be raised up to the height of divine contemplation; and this we have marked in the fact, that Jesus went in to a mountain apart to pray.

(ut sup.) But mark the great carefulness of the Evangelist. He not only says that the holy Apostles were chosen, but he enumerates them by name, that no one should dare to insert any others in the catalogue; Simon, whom he also called Peter, and Andrew his brother.

But if we may learn the interpretation of the Apostles' names, know that Peter means, "loosening or knowing;" Andrew, "glorious power," or "answering;" but James, "apostle of grief;" John, "the grace of the Lord;" Matthew, "given;" Philip, "large mouth," or the "orifice of a torch;" Bartholomew, "the son of him who lets down water;" Thomas, "deep or twin;" James the son of Alphæus, "supplanter of the step of life;" Judas, "confession;" Simon, "obedience."

[AD 735] Bede on Luke 6:12
But it happened in those days that He went out to the mountain to pray. Not everyone who prays ascends to the mountain. For there is a prayer that brings about sin. But he who prays well, who seeks God in prayer, ascends from earthly things to higher things, reaching the peak of higher concern. But he who earnestly prays about riches, or worldly honor, or even about the death of an enemy, he, lying in the depths, sends vile prayers to God. The Lord, however, prays not for Himself, but to intercede for me. For even if the Father has put all things in the Son’s power, the Son still deems it necessary to beseech the Father on our behalf because He is our advocate. For He says, "We have an advocate with the Father, Jesus Christ" (1 John 2). If He is an advocate, He must intervene for my sins. Therefore, He pleads not as a weak person, but as a pious one. Do you want to know how capable He is of accomplishing everything He wishes? He is both advocate and judge. In one, the function of piety; in the other, the symbol of power.

[AD 735] Bede on Luke 6:12
And He was spending the night in prayer to God. A model is prescribed for you to emulate. What should you do for your own salvation when Christ spends the night in prayer for you? What should you do when you wish to undertake an office of piety, when Christ ensured to pray first before sending the apostles? Do you want to know how, He prayed for me, not for Himself?

[AD 735] Bede on Luke 6:12-16
He not only surnamed Peter first, but long before this, when he was brought by Andrew, it is said, Thou shall be called Cephas, which is by interpretation, a stone (John 1:42.). But Luke, wishing to mention the names of the disciples, since it was necessary to call him Peter, wished shortly to imply that this was not his name before, but the Lord had given it to him.

Matthew places himself after his fellow-disciple Thomas, from humility, whereas by the other Evangelists he is put before him. It follows, James the son of Alphæus, and Simon who is called Zelotes.

But in a mystical sense the mountain on which our Lord chose His disciples represents the loftiness of justice in which they were to be instructed, and which they were to preach to others; so also the law was given on a mountain.

[AD 1274] Glossa Ordinaria on Luke 6:12-16
(non occ.) When adversaries rose up against the miracles and teaching of Christ, He chose Apostles as defenders and witnesses of the truth, and prefaces their election with prayer; as it is said, And it came to pass, &c.

Because in truth he was of Cana in Galilee, which is interpreted zeal; and this is added to distinguish him from Simon Peter. It follows, Judas the brother of James, and Judas Iscariot, who also betrayed him.