But those things which proceed out of the mouth,.... Meaning not material things, as spittle, vomit, c. but, as it follows, which
come forth from the heart: are first conceived and formed there, and then come forth from thence, and are expressed by the mouth as all idle words, foolish talking, filthy jesting, unsavoury communication, and every word that is rotten and corrupt, or which is done in the life and conversation;
and they defile the man: the heart is the corrupt fountain from whence all moral defilement flows; and sinful words and actions are the impure streams, which spring from thence, and increase the moral pollution of human nature.