From: Luke 2:1-14
The Birth of Jesus
 In those days a decree went out from Caesar Augustus that all the world should be enrolled.  This was the first enrollment, when Quirinius was governor of Syria.  And all went to be enrolled, each to his own city.  And Joseph also went up from Galilee, from the city of Nazareth, to Judea, to the city of David, which is called Bethlehem, because he was of the house and lineage of David,  to be enrolled with Mary, his betrothed, who was with child.  And while they were there, the time came for her to be delivered.  And she gave birth to her first-born son and wrapped Him in swaddling cloths, and laid Him in a manger, because there was no place for them in the inn.
The Adoration of the Shepherds
 And in that region there were shepherds out in the field, keeping watch over their flock by night.  And an angel of the Lord appeared to them, and the glory of the Lord shone around them, and they were filled with fear.  And the angel said to them, "Be not afraid; for behold, I bring you good news of great joy which will come to all the people;  for to you is born this day in the city of David, a Savior, who is Christ the Lord.  And this will be a sign for you: you will find a babe wrapped in swaddling cloths and lying in a manger."  And suddenly there was with the angel a multitude of heavenly hosts praising God and saying,  "Glory to God in the highest, and on earth peace among men with whom He is pleased!"
1. Caesar Augustus was Roman emperor at this time, reigning from 30 B.C. to A.D. 14. He is known to have commissioned various censuses, one of which could well be that referred to by the evangelist. Since Rome normally respected local usages, censuses were carried out in line with Jewish custom whereby every householder went to his place of origin to be listed in the census.
6-7. The Messiah is born, the Son of God and our Savior. "He made Himself a child [...] to enable you to become a perfect man; He was wrapped in swaddling clothes to free you from the bonds of death [...]. He came down on earth to enable you to rise up to Heaven; He had no place in the inn so that you might have many mansions in Heaven. He, being rich, became poor for our sake--St. Paul says (2 Corinthians 8:9)--so as to enrich us with His poverty [...]. The tears of this crying child purify men, they wash away my sins" (St. Ambrose, "Expositio Evangelii Sec. Lucam, in loc.").
The new-born Child does not yet speak, but He is the eternal Word of the Father. Even from the manger in Bethlehem He teaches us. "We must learn the lessons which Jesus teaches us, even when He is just a newly born child, from the very moment He opens His eyes on this blessed land of men" (J. Escriva, "Christ Is Passing By", 14). The main lesson He gives us concerns humility: "God humbled Himself to allow us to get near Him, so that we could give our love in exchange for His, so that our freedom might bow, not only at the sight of His power, but also before the wonder of His humility.
"The greatness of this Child who is God! His Father is the God who has made Heaven and earth and there He is, in a manger, `because there was no room at the inn' (Luke 2:7); there was nowhere else for the Lord of all creation" (J. Escriva, "Christ Is Passing By", 18).
Our hearts should provide Jesus with a place where He can be born spiritually; that is, we should be born to a new life, becoming a new creature (Romans 6:4), keeping that holiness and purity of soul which we were given in Baptism and which is like being born again. We contemplate the birth of our Savior when we pray the "third mystery" of the Holy Rosary.
7. "First-born son": it is usual for Sacred Scripture to refer to the first male child as "the first-born" whether or not there were other brothers (cf., for example, Exodus 13:2; 13:13; Numbers 15:8; Hebrews 1:6). The same practice is to be found in ordinary speech; take, for example, this inscription dating from approximately the same time as Christ was born, which was found near Tell-el-Jedvieh (in Egypt) in 1922, which states that a woman named Arsinoe died while giving birth to "her first-born son". Otherwise, as St. Jerome explains in his letter "Adversus Helvidium", 10, "if only He were first-born who was followed by other brothers, He would not deserve the rights of the first-born, which the Law lays down, until the other had been born"--which would be absurd, since the Law ordains that those first-born should be "ransomed" within a month of their birth (Numbers 18:16).
However, Jesus Christ is first-born in a much deeper sense independent of natural or biological considerations--which St. Bede describes in these words, summarizing a long tradition of the Fathers of the Church: "Truly the Son of God, who was made manifest in the flesh, belongs to a more exalted order not only because He is the Only-begotten of the Father by virtue of the excellence of His divinity; He is also first-born of all creatures by virtue of His fraternity with men: concerning this [His primogeniture] it is said: `For those whom He foreknew He also predestined to be conformed to the image of His Son, in order that He might be the first-born among many brethren' (Romans 8:29). And concerning the former [His being the Only-begotten] it is said `we have beheld His glory, glory as of the only Son from the Father' (John 1:14). Thus, He is only-begotten by the substance of the Godhead, and first-born through His assumption of humanity; first-born by grace, only-begotten by nature. This is why He is called brother and Lord; brother, because He is the first-born; Lord, because He is the Only-begotten" ("In Lucae Evangelium Expositio, in loc.").
Christian Tradition teaches, as a truth of faith, that Mary remained a virgin after Christ's birth, which is perfectly in keeping with Christ's status as her first-born. See, for example, these words of the Lateran Council of 649: "If anyone does not profess according to the holy Fathers that in the proper and true sense the holy, ever-Virgin, immaculate Mary is the Mother of God, since in this last age not with human seed but of the Holy Spirit she properly and truly conceived the divine Word, who was born of God the Father before all ages, and gave Him birth without any detriment to her virginity, which remained inviolate even after His birth: let such a one be condemned" (Canon 3).
8-20. At His birth Christ's divinity and His humanity are perfectly manifested: we see His weakness--the form of a servant (Philippians 2:7)--and His divine power. Christian faith involves confessing that Jesus Christ is true God and true man.
The salvation which Christ brought us is offered to everyone, without distinction: "Here there cannot be Greek and Jew, circumcised or uncircumcised, barbarian, Scythian, slave, free man, but Christ is all, and in all" (Colossians 3:11). That is why, even at His birth, He chose to manifest Himself to different kinds of people--the shepherds, the Magi and Simeon and Anna. As St. Augustine comments: "The shepherds were Israelites; the Magi, Gentiles. The first lived near-by; the latter, far away. Yet both came to the cornerstone, Christ" ("Sermo De Nativitate Domini", 202).
8-9. These shepherds may have been from the neighborhood of Bethlehem or even have come from further afield in search of pasture for their flocks. It was these simple and humble people who were the first to hear the good news of Christ's birth. God has a preference for the humble (cf. Proverbs 3:32); He hides from those who consider themselves wise and understanding and reveals Himself to "babes" (cf. Matthew 11:25).
10-14. The angel announces that the new-born Child is the Savior, Christ the Lord. He is the "Savior" because He has come to save us from our sins (cf. Matthew 1:21). He is "the Christ", that is, the Messiah so often promised in the Old Testament, and now born among us in fulfillment of that ancient hope. He is "the Lord": this shows Christ's divinity, for this is the name God chose to be known by to His people in the Old Testament, and it is the way Christians usually refer to and address Jesus and the way the Church always confesses her faith: "We believe [...] in one Lord, Jesus Christ, the only Son of God."
When the angel tells them that the Child has been born in the city of David, he reminds them that this was where the Messiah Redeemer was supposed to be born (cf. Micah 5:2; Matthew 2:6), who would be a descendant of David (cf. Psalm 110:1-2; Matthew 22:42-46).
Christ is the Lord not only of men but also of angels, which is why the angels rejoice at His birth and render Him the tribute of adoration: "Glory to God in the highest." And, since men are called to share, like them, in the happiness of Heaven, the angels add: "And on earth peace among men with whom He is pleased." "They praise the Lord," St. Gregory the Great comments, "putting the notes of their hymn in harmony with our redemption; they see us as already sharing in their own happy destiny and rejoice at this" ("Moralia", 28, 7).
St. Thomas explains why the birth of Christ was revealed through angels: "What is in itself hidden needs to be manifested, but not what is in itself manifest. The flesh of Him who was born was manifest, but His Godhead was hidden, and therefore it was fitting that this birth should be made known by angels, who are ministers of God. This is why a certain brightness accompanied the angelic apparition, to indicate that He who was just born `reflects the glory of the Father' (Hebrews 1:3)" ("Summa Theologiae", III, q. 36, a. 5 ad 1).
The angel also tells the shepherds that Christ is a man: "You will find the babe wrapped in swaddling cloths and lying in a manger" (verse 12)--as foretold in the Old Testament: "To us a child is born, to us a son is given; and the government will be upon his shoulder" (Isaiah 9:6).
14. This text can be translated in two ways, which are compatible with each other. One is the version chosen by the RSV; the other, as an RSV note points out: "other ancient authorities read `peace, good will among men'"; a variant is the translation used in the Liturgy: "Peace on earth to men who are God's friends." Essentially what the text says is that the angels ask for peace and reconciliation with God, which is not something which results from men's merits but rather comes from God's deigning to have mercy on them. The two translations are complementary, for when men respond to God's grace they are fulfilling God's good will, God's love for them: "Iesus Christus, Deus homo": Jesus Christ, God-man. This is one of `the mighty works of God' (Acts 2:11), which we should reflect upon and thank Him for. He has come to bring peace on earth to men of good will' (Luke 2:14), to all men who want to unite their wills to the holy will of God" (J. Escriva, "Christ Is Passing By", 13).
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.