From: Mark 7:1-8, 14-15, 21-23
The Tradition of the Elders
 Now when the Pharisees gathered together to Him (Jesus), with some of the scribes, who had come from Jerusalem,  they saw that some of His disciples ate with hands defiled, that is, unwashed.  (For the Pharisees, and all the Jews, do not eat unless they wash their hands, observing the tradition of the elders;  and when they come from the market place, they do not eat unless they purify themselves; and there are many other traditions which they observe, the washing of cups and pots and vessels of bronze.)  And the Pharisees and the scribes asked Him, "Why do Your disciples not live according to the tradition of the elders, but eat with hands defiled?"  And He said to them, "Well did Isaiah prophesy of you hypocrites, as it is written, `This people honors Me with their lips, but their heart is far from Me;  in vain do they worship Me, teaching as doctrines the precepts of men.'  You leave the commandment of God, and hold fast the tradition of men.
What Defiles a Man
 And He (Jesus) called the people to meet Him, and said to them, "Hear Me, all of you, and understand:  there is nothing outside a man which by going into him can defile him; but the things that come out of a man are what defile him."  For from within, out of the heart of man, come evil thoughts, fornication, theft, murder, adultery,  coveting, wickedness, deceit, licentiousness, envy, slander, pride, foolishness.  All these evil things come from within, and they defile a man.
1-2. Hands were washed not for reasons of hygiene or good manners but because the custom had religious significance: it was a rite of purification. In Exodus 30:17ff the Law of God laid down how priests should wash before offering sacrifice. Jewish tradition had extended this to all Jews before every meal, in an effort to give meals a religious significance, which was reflected in the blessings which marked the start of meals. Ritual purification was a symbol of the moral purity a person should have when approaching God (Psalm 24:3ff; 51:4 and 9); but the Pharisees had focused on the mere external rite. Therefore Jesus restores the genuine meaning of these precepts of the Law, whose purpose is to teach the right way to render homage to God (cf. John 4:24).
3-5. We can see clearly from this text that very many of those to whom St. Mark's Gospel was first addressed were Christians who had been pagans and were unfamiliar with Jewish customs. The Evangelist explains these customs in some detail, to help them realize the significance of the events and teachings reported in the Gospel story.
Similarly, Sacred Scripture needs to be preached and taught in a way which puts it within reach of its hearers. This is why Vatican II teaches that "it is for the bishops suitable to instruct the faithful [...] by giving them translations of the sacred texts which are equipped with necessary and really adequate explanations. Thus the children of the Church can familiarize themselves safely and profitably with the Sacred Scriptures, and become steeped in their spirit" ("Dei Verbum", 25).
15. Some important codexes add here: "If any man has ears to hear, let him hear," which would form verse 16.
20-23. "In order to help us understand divine things, Scripture uses the _expression `heart' in its full meaning, as the summary and source, _expression and ultimate basis, of one's thoughts, words and actions" ([St] J. Escriva, "Christ Is Passing By", 164).
The goodness or malice, the moral quality, of our actions does not depend on their spontaneous, instinctive character. The Lord Himself tells us that sinful actions can come from the human heart.
We can understand how this can happen if we realize that, after original sin, man "was changed for the worse" in both body and soul and was, therefore, prone to evil (cf. Council of Trent, "De Peccato Originali"). Our Lord here restores morality in all its purity and intensity.
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.