From: Luke 6:12-19
The Calling of the Apostles
 In these days He (Jesus) went out into the hills to pray; and all night He continued in prayer to God.  And when it was day, He called His disciples, and chose from them twelve, whom He named Apostles:  Simon, whom He named Peter, and Andrew, his brother, and James and John, and Philip and Bartholomew,  and Matthew, and Thomas, and James the son of Alphaeus, and Simon who was called the Zealot,  and Judas the son of James, and Judas Iscariot, who became a traitor.
The Sermon on the Mount
 And He came down with them and stood on a level place, with a great crowd of His disciples and a great multitude of people from all Judea and Jerusalem and the sea coast of Tyre and Sidon, who came to hear Him and to be healed of their diseases;  and those who were troubled with unclean spirits were cured.  And all the crowd sought to touch Him, for power came forth from Him and healed them all.
12-13. The evangelist writes with a certain formality when describing this important occasion on which Jesus chooses the Twelve, constituting them as the apostolic college: "The Lord Jesus, having prayed at length to the Father, called to Himself those whom He willed and appointed twelve to be with Him, whom He might send to preach the King dom of God (cf. Mark 2:13-19; Matthew 10:1-42). These Apostles (cf. Luke 6:13) He constituted in the form of a college or permanent assembly, at the head of which He placed Peter, chosen from among them (cf. John 21:15-17). He sent them first of all to the children of Israel and then to all peoples (cf. Romans 1:16), so that, sharing in His power, they might make all peoples His disciples and sanctify and govern them (cf. Matthew 28:16-20; and par.) and thus spread the Church and, administering it under the guidance of the Lord, shepherd it all days until the end of the world (cf. Matthew 28:20). They were fully confirmed in this mission on the day of Pentecost (cf. Act 2:1-26) [...]. Through their preaching the Gospel everywhere (cf. Mark 16:20), and through its being welcomed and received under the influence of the Holy Spirit by those who hear it, the Apostles gather together the universal Church, which the Lord founded upon the Apostles and built upon Blessed Peter their leader, the chief cornerstone being Christ Jesus Himself (cf. Revelation 21:14; Matthew 16:18; Ephesians 2:20). That divine mission, which was committed by Christ to the Apostles, is destined to last until the end of the world (cf. Matthew 28:20), since the Gospel, which they were charged to hand on, is, for the Church, the principle of all its life for all time. For that very reason the Apostles were careful to appoint successors in this hierarchically constituted society" (Vatican II, "Lumen Gentium", 19-20).
Before establishing the apostolic college, Jesus spent the whole night in prayer. He often made special prayer for His Church (Luke 9:18; John 17:1ff), thereby preparing His Apostles to be its pillars (cf. Galatians 2:9). As His Passion approaches, He will pray to the Father for Simon Peter, the head of the Church, and solemnly tell Peter that He has done so: "But I have prayed for you that your faith may not fail" (Luke 22:32). Following Christ's example, the Church stipulates that on many occasions liturgical prayer should be offered for the pastors of the Church (the Pope, the bishops in general, and priests) asking God to give them grace to fulfill their ministry faithfully.
Christ is continually teaching us that we need to pray always (Luke 18:1). Here He shows us by His example that we should pray with special intensity at important moments in our lives. "`Pernoctans in oratione Dei. He spent the whole night in prayer to God.' So St.Luke tells of our Lord. And you? How often have you persevered like that? Well, then...." ([Blessed] J. Escriva, "The Way", 104).
On the need for prayer and the qualities our prayer should have, see the notes on Matthew 6:5-6; 7:7-11; 14:22-23; Mark 1:35; Luke 5:16; 11:1-4; 22:41-42.
12. Since Jesus is God, why does He pray? There were two wills in Christ, one divine and one human (cf. "St. Pius X Catechism", 91), and although by virtue of His divine will He was omnipotent, His human will was not omnipotent. When we pray, what we do is make our will known to God; therefore Christ, who is like us in all things but sin (Hebrews 4:15), also had to pray in a human way (cf. "Summa Theologiae", III, q. 21, a. 1). Reflecting on Jesus at prayer, St. Ambrose comments: "The Lord prays not to ask things for Himself, but to intercede on my behalf; for although the Father has put everything into the hands of the Son, still the Son, in order to behave in accordance with His condition as man, considers it appropriate to implore the Father for our sake, for He is our Advocate [...]. A Master of obedience, by His example He instructs us concerning the precepts of virtue: `We have an advocate with the Father' (1 John 2:1)" ("Expositio Evangelii sec. Lucam, in loc.").
14-16. Jesus chose for Apostles very ordinary people, most of them poor and uneducated; apparently only Matthew and the brothers James and John had social positions of any consequence. But all of them gave up whatever they had, little or much as it was, and all of them, bar Judas, put their faith in the Lord, overcame their shortcomings and eventually proved faithful to grace and became saints, veritable pillars of the Church. We should not feel uneasy when we realize that we too are low in human qualities; what matters is being faithful to the grace God gives us.
19. God became man to save us. The divine person of the Word acts through the human nature which He took on. The cures and casting out of devils which He performed during His life on earth are also proof that Christ actually brings redemption and not just hope of redemption. The crowds of people from Judea and other parts of Israel who flock to Him, seeking even to touch Him, anticipate, in a way, Christians' devotion to the holy Humanity of Christ.
Source: "The Navarre Bible: Text and Commentaries". Biblical text taken from the Revised Standard Version and New Vulgate. Commentaries made by members of the Faculty of Theology of the University of Navarre, Spain. Published by Four Courts Press, Kill Lane, Blackrock, Co. Dublin, Ireland. Reprinted with permission from Four Courts Press and Scepter Publishers, the U.S. publisher.