From: Matthew 19:3-12
Marriage and Virginity
 And Pharisees came up to Him (Jesus) and tested Him by asking, "Is it lawful to divorce one's wife for any cause?"  He answered, "Have you not read that He who made them from the beginning made them male and female,  and said, `For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one'?  So they are no longer two but one. What therefore God has joined together, let no man put asunder."  They said to Him, "Why then did Moses command one to give a certificate of divorce, and to put her away?"  He said to them, "For your hardness of heart Moses allowed you to divorce your wives, but from the beginning it was not so.  And I say to you: whoever divorces his wife, except for unchastity, and marries another, commits adultery; and he who marries a divorced woman commits adultery."
 The disciples said to Him, "If such is the case of a man with his wife, it is not expedient to marry."  But He said to them, "Not all men can receive this precept, but only those to whom it is given.  For there are eunuchs who have been so from birth, and there are eunuchs who have been made eunuchs by men, and there are eunuchs who have made themselves eunuchs for the sake of the Kingdom of Heaven. He who is able to receive this, let him receive it."
4-5. "Marriage and married love are by nature ordered to the procreation and education of children. Indeed children are the supreme gift of marriage and greatly contribute to the good of the parents themselves. God Himself said: `It is not good that man should be alone' (Genesis 2:18), and `from the beginning (He) made them male and female' (Matthew 19:4); wishing to associate them in a special way with his own creative work, God blessed man and woman with the words: `Be fruitful and multiply' (Genesis 1:28). Without intending to underestimate the other ends of marriage, it must be said that true married life and the whole structure of family life which results from it is directed to disposing the spouses to cooperate valiantly with the love of the Creator and Savior, who through them will increase and enrich His family from day to day" (Vatican II, "Gaudium Et Spes", 50).
9. Our Lord's teaching on the unity and indissolubility of marriage is the main theme of this passage, apropos of which St. John Chrysostom comments that marriage is a lifelong union of man and woman (cf. "Hom. on St. Matthew", 62). On the meaning of "except for unchastity", see the note on Matthew 5:31-32).
11. "Not all men can receive this precept": our Lord is fully aware that the demands involved in His teaching on marriage and His recommendation of celibacy practised out of love of God run counter to human selfishness. That is why He says that acceptance of this teaching is a gift from God.
12. Our Lord speaks figuratively here, referring to those who, out of love for Him, renounce marriage and offer their lives completely to Him. Virginity embraced for the love of God is one of the Church's most precious charisms (cf. 1 Corinthians 7); the lives of those who practise virginity evoke the state of the blessed in Heaven, who are like the angels (cf. Matthew 22:30). This is why the Church's Magisterium teaches that the state of virginity for the sake of the Kingdom of Heaven is higher than the married state (cf. Council of Trent, "De Sacram. Matr.", can. 10; cf. also Pius XII, "Sacra Virginitas"). On virginity and celibacy the Second Vatican Council teaches: "The Church's holiness is also fostered in a special way by the manifold counsels which the Lord proposes to His disciples in the Gospel for them to observe. Towering among these counsels is that precious gift of divine grace given to some by the Father (cf. Matthew 19:11; 1 Corinthians 7:7) to devote themselves to God alone more easily in virginity or celibacy [...]. This perfect continence for love of the Kingdom of Heaven has always been held in high esteem by the Church as a sign and stimulus of love, and as a singular source of spiritual fertility in the world" ("Lumen Gentium", 42; cf. "Perfectae Caritatis", 12). And, on celibacy specifically, see Vatican II's "Presbyterorum Ordinis", 16 and "Optatam Totius", 10.
However, both virginity and marriage are necessary for the growth of the Church, and both imply a specific calling from God: "Celibacy is precisely a gift of the Spirit. A similar though different gift is contained in the vocation to true and faithful married love, directed towards procreation according to the flesh, in the very lofty context of the sacrament of Matrimony. It is obvious that this gift is fundamental for the building up of the great community of the Church, the people of God. But if this community wishes to respond fully to its vocation in Jesus Christ, there will also have to be realized in it, in the correct proportion, that other gift, the gift of celibacy `for the sake of the Kingdom of Heaven'" (John Paul II, "Letter To All Priests", 1979).
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.