Matt 15: What penalty for not washing hands? In Matthew 15:2, the Pharisees accuse the disciples of Jesus of not properly washing their hands before eating.


  “Why do your disciples break the tradition of the elders? For they do
  not wash their hands when they eat.”


What, if any, penalty or punishment could the disciples have incurred from the Pharisees had Jesus not refuted this accusation?
According to the rabbinical interpretation of Ex. 34:27,34 (and others) God gave to Moses other laws and maxims orally, as well as verbal explanations of the written law, enjoining him not to record these teachings, but to deliver them to the people by word of mouth. Most modern Jewish traditions descend from the Pharisees with the notable exception of Karaite Judaism. There were many Jewish sects at the time of Christ with the main branches being Sadducee, Pharisees, Essene and Zealot. A close examination of Jesus's teachings would place him somewhere between the Pharisee and Essene with an apocalyptic emphasis -- or maybe the Gandi of the Zealot movement, where he would agree with their apocalyptic beliefs while abhorring their violent tendencies.

According to the Gospels, he upbraided the Pharisees for their oral traditions and even went so far as to say their oral law was a rejection, breaking or voiding of the written law. As Christianity and rabbinical Judaism shaped each other during the first few centuries of the common era, the rabbinical interpretations of the oral law eventually came to be written down, in spite of the fact that during Second Temple Judaism many Pharisees believed it was against God's law for them to be put into writing.

Ritual hand-washing is from these "added" laws from the oral tradition. Using asmachta, (a Biblical hint, rather than an explicit requirement) the Talmud used the requirement of washing the hands in Leviticus 15:11 as a hint for hand-washing in general. Leviticus 15:11 only speaks about washing the hands after they have been in contact with an issue of bodily fluid and the only penalty or punishment mentioned is being considered ritually impure until sundown. Ritual purity was important to many Jews to the extent of breaking the second commandment which we often call the Golden Rule. This is the reason Jesus praises the actions of a Samaritan to implicate the priest and Levite (same thing, two different people and never mind that most Second Temple Levitical priests were Sadducee, not Pharisee) who would not show compassion for the victim of the robbery who was lying bleeding on the side of the road in the parable, because his blood would have make them ritually unclean.

So, other than social ostracism, the disgust and disdain of the Pharisees and being temporarily barred from attendance at the Temple, there is no recorded punishment or penalty to be meted out for the offense.