From: Matthew 19:16-22
The Rich Young Man
 And behold, one man came up to Him (Jesus), saying, "Teacher, what good deed must I do, to have eternal life?"  And He said to him, "Why do you ask Me about what is good? One there is who is good. If you would enter life, keep the commandments."  He said to Him, "Which?" And Jesus said, "You shall not kill, You shall not commit adultery, You shall not steal, You shall not bear false witness,  Honor your father and mother, and, You shall love your neighbor as yourself."  The young man said to Him, "All these I have observed; what do I still lack?"  Jesus said to him, "If you would be perfect, go, sell what you possess and give to the poor, and you will have treasure in Heaven; and come, follow Me."  When the young man heard this he went away sorrowful; for he had great possessions.
17. The Vulgate and other translations, supported by a good many Greek codexes, fill this verse out by saying, "One alone is good, God."
20-22. "What do I still lack?" The young man kept the commandments that were necessary for salvation. But there is more. This is why our Lord replies, "if you would be perfect..." that is to say, if you want to acquire what is still lacking to you. Jesus is giving him an additional calling, "Come, follow Me": He is showing that He wants him to follow Him more closely, and therefore He requires, as He does others (cf. Matthew 4:19-22), to give up anything that might hinder his full dedication to the Kingdom of God.
The scene ends rather pathetically: the young man goes away sad. His attachment to his property prevails over Jesus' affectionate invitation. Here is sadness of the kind that stems from cowardice, from failure to respond to God's calling with personal commitment.
In reporting this episode, the evangelists are actually giving us a case-study which describes a situation and formulates a law, a case-study of specific divine vocation to devote oneself to God's service and the service of all men.
This young man has become a symbol of the kind of Christian whose mediocrity and shortsightedness prevent him from turning his life into a generous, fruitful self-giving to the service of God and neighbor.
What would this young man have become, had be been generous enough to respond to God's call? A great apostle, surely.
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.