From: Matthew 9:14-15
The Call of Matthew (Continuation)
 Then the disciples of John (the Baptist) came to Him (Jesus), saying, "Why do we and the Pharisees fast, but Your disciples do not fast?"  And Jesus said them, "Can the wedding guests mourn as long as the bridegroom is with them? The days will come, when the bridegroom is taken away from them, and then they will fast."
14-17. This passage is interesting, not so much because it tells us about the sort of fasting practised by the Jews of the time--particularly the Pharisees and John the Baptist's disciples--but because of the reason Jesus gives for not requiring His disciples to fast in that way. His reply is both instructive and prophetic. Christianity is not a mere mending or adjusting of the old suit of Judaism. The redemption wrought by Jesus involves a total regeneration. Its spirit is too new and too vital to be suited to old forms of penance, which will no longer apply.
We know that in our Lord's time Jewish theology schools were in the grip of a highly complicated casuistry to do with fasting, purifications, etc., which smothered the simplicity of genuine piety. Jesus' words point to that simplicity of heart with which His disciples might practise prayer, fasting and almsgiving (cf. Matthew 6:1-18 and notes to same). From apostolic times onwards it is for the Church, using the authority given it by our Lord to set out the different forms fasting should take in different periods and situations.
15. "The wedding guests": literally, "the sons of the house where the wedding is being celebrated"--an _expression meaning the bridegroom's closest friends. This is an example of how St. Matthew uses typical Semitic turns of phrase, presenting Jesus' manner of speech.
This "house" to which Jesus refers has a deeper meaning; set beside the parable of the guests at the wedding (Matthew 22:1 ff), it symbolizes the Church as the house of God and the body of Christ: "Moses was faithful in all God's house as a servant, to testify to the things that were to be spoken later, but Christ was faithful over God's house as a son. And we are His house if we hold fast our confidence and pride in our hope" (Hebrews 3:5-6).
The second part of the verse refers to the violent death Jesus would meet.
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.