"Nothing that enters one from outside can defile that person;
but the things that come out from within are what defile."
Purity is a word that few would consider pejorative; it sits alongside other words we associate with virtue such as honesty, courage, etc. It is even more effective as a marketing tool to entice the consumer that you are getting 100% of what you are expecting. The other word associated with this one is perfection. In a sense, purity is a type of perfection, and when you begin an endeavor, it common to hope for perfection.
It is this struggle to be perfect before God that the Jews turned to Torah (the first five books of the Bible). These books contain a little over six-hundred laws that were composed between 600 and 400 BCE. These laws were extended to interpretive texts that were designed to help people apply these laws to everyday life to keep better the original six-hundred or so laws in Torah. By Jesus' time, some of these laws became impediments to the spirit that informed them. Like so many good ideas, when people who have lost sight of why the law exists simply follow the law "because it is the law", the spirit suffers the ignorance of the law-abiding.
In today's gospel, those whose job it was to interpret and admonish adherence to the Law (Pharisees and scribes) were incensed that Jesus seemed oblivious to the demands of the Law. He did not seem to chastise those among his disciples that did not wash before meals in violation, not of the law, per se (Leviticus 15:11), but explicitly from the Talmud, a group of interpretive statements to apply the Law. When questioned as to why Jesus seemed such a scoff-law we get a two part answer: You are like the hypocrites of whom Isaiah speaks "They honor me with their lips; but their hearts are far from me", and the spiritual insight that "Nothing that enters one from outside can defile that person; but the things that come out from within are what defile."
Jesus' statement in the fifth chapter of Matthew intends not to abolish the law but to fulfill it, and now he seems clear as to how the Law is fulfilled: intention.
The other day, I had a rather distressing conversation with a man who insisted that undocumented immigrants should not be allowed to receive any public services such as education and a driver's license. He said this about the poor entering our southern border. He felt quite confident that his view wasn't obstructed by racism, but that "it was the law". He insisted that being acting unlawfully was the fundamental transgression that could only be remedied by these people returning to their native country, and following the procedure for properly entering the United States. He was so focused on the violation of the law that the broader question of justice seemed to him as a distraction from the core issue of these folks breaking the law.
The law serves justice, but so many today have it reversed thinking that if it is law it presupposes being just. Needless to say, in recent memory laws that kept blacks segregated from society, women from voting, and prohibiting consenting adults who are gay from marrying are examples of laws most would find difficult to reconcile with concepts of justice.
Jesus understood this insidious tendency to focus on law rather than justice.This focus provides a false sense of comfort to those who don't want to deal with the messiness of justice and opt for the simplistic purity of law. For many Christians, the Bible has become the modern equivalent to the religious law--studied to discover transgression rather than compassion in the false promise that by doing so one may become perfect. But perfection does not lie in the observance of the law, but in its fulfillment as Christ fulfilled it: love of God and love of neighbor--the two most important commandments according to Jesus.