They noticed that some of his disciples were eating their food with hands that were ritually unclean - that is, they had not washed them in the way the Pharisees said people should.
(For the Pharisees, as well as the rest of the Jews, follow the teaching they received from their ancestors: they do not eat unless they wash their hands in the proper way;
nor do they eat anything that comes from the market unless they wash it first. a And they follow many other rules which they have received, such as the proper way to wash cups, pots, copper bowls, and beds. b)