The word translated as "defile" means "communicate" and "make common." Calling a person "common" is a bit of an insult today, but it could be heard more critically in Jesus's time, especially when talking about the "pharisees," that is, the "distinguished." However, there is a kind of logic that got the KJV translators to the concept of "defile," though their idea wasn't what Christ's listeners heard.  In Jewish custom, items dedicated to God were kept separate from everyday items. The Hebrew word translated as "holy" means "separate." Its opposite was the word for "common." It did not mean "defiled" and "impure" as it is often translated, as much it means as a regular, everyday thing that everyone used rather than a special, separate thing that was dedicated to God. So Jesus is making a play on the Jewish idea of "common" as not suitable for God with the Greek word for common meaning "communicate" and sharing ideas.

The verbs translated as "comes" and "goes" are reversed, based upon their root words. However, these words should not be translated simply as “comes” and “goes” because they are compound words, with prefixes. And both words are followed by prepositions the same as their prefixes. This is typical Jesus wordplay to emphasize his point. Both are also participle, with endings of “-ing.” He says something like “the incoming into” and “the outgoing out.“ But his listeners heard the repetition of the prefix before and the preposition after. As I have pointed out in this article, repetition is a key element of his humor.

Jesus doesn't say this about "a man" but a specific man, "the man" or "this man." He may well be talking about his mouth.