Mat 15:18 But those things which proceed out of the mouth come from the heart; and they defile the man.

As we discussed in 15:11, this word "defile" is completely misleading here. The idea really means "to communicate" and "to impart." It means "make common knowledge." What Christ is saying here is that what comes from our hearts determines who we are to others and to God. The "heart" is Christ's symbol for relationships and feeling. The source of what we share with people is what we feel about people.

Notice how Christ never mentions words or thoughts or hearing. All of those metaphors would put this context in the mental realm rather than the emotional realm of relationships. It is people's caring, not their ideas, that ends up measuring them as people.

"Defiles" is from koinoô, which means "to communicate," "to impart," "to share." Only in Matthew is it translated as "defile."