Please read the passage before reading the homily
We know that we are supposed to wash our hands before eating. Our parents taught us this. We learned to wash to get rid of germs that could make us sick. Our hands do a good job of touching germs throughout the day.
In the time of Jesus, it was a religious obligation to wash the hands. The religious reason may have been to prevent the spread of germs, but the ancients had very little knowledge of germs. The religious obligation protected people from germs, but it was primarily as a religious obligation that people washed their hands.
When we eat, we put food into our mouths. It does not matter whether the food has been washed or not because it all goes to the place. It all goes down the throat, into the stomach and through the digestive tract and so on. It does not go into the heart or thinking organs.
What comes out of our mouths, however, comes from the inner core of our being. It comes from our minds and wills, from our thinking and doing capacities. This is where evil comes, from what we put out of the mouth, not what we put into it.
Jesus is teaching more about the source of our evil than about what we eat. The chief point is not about washing before eating, but that our evil actions come from within us, not from without us: we are responsible for our actions (The devil cannot make us do it). In a sense, Jesus’ attitude was that if the disciples wanted to eat with dirty hands, that was okay. If they wanted to talk or act in evil ways, this was not okay. Nothing that enters from outside can defile, but only what comes from within can defile.