Having delivered this stinging rebuke to the scribes and Pharisees, Christ proceeds to explain what is the fount of heresies, false doctrine, and every other manner of evil: namely, the human heart.  He declared that it is not that which enters into the mouth which defiles a man, but that which comes out of it.  The Lord’s own disciples seemed not to understand this saying, but apparently the Pharisees did, because they were offended.  But Christ was not interested in the praise of men.  He came to preach the truth, and if it offended His hearers, so be it.  “Every plant which my heavenly Father hath not planted shall be rooted up.”  The plain inference was that the Pharisees were not plants of His Father’s planting, as their false doctrine gave evidence.  Therefore, they must be rooted up and destroyed.  More than this, they were blind men leading blind men.  They thought that they were teachers of the law, guides of God’s people.  But in reality they were staggering blindly alongside the edge of the pit of destruction, and leading other blind men along with them.  Those who continued to follow the blind Pharisees, rather than turning after Christ, must of necessity fall into the ditch of eternal perdition.

The disciples requested an explanation of this parable, apparently referring primarily to Christ’s statement concerning that which goes in and comes out of the mouth.  The explanation is simple, and very noteworthy.  The things that enter into our mouth do not communicate sin to us, but are simply digested and then evicted from the body.  But the things which come out of our mouths manifest what is in our hearts.  It is these things which defile the man.  Truly, “the tongue is a fire, a world of iniquity.” 

Jesus proceeds to give a dreadful litany of the fruits of the heart: evil thoughts, murders, adulteries, fornications, thefts, false witness, blasphemies.”  The Pharisees were more concerned about people eating with unwashen hands than they were about these horrible fruits of the unrenewed heart.  The reason is, of course, because their hearts were still dead in trespasses and sins, and they thought themselves good and righteous while in reality they were still children of wrath, even as others.  Their words betrayed the corruption and vileness that still existed in their hearts.  So it will be with all unregenerate men.  Only by the grace of God can we communicate good things from our hearts, for until we are given a new mind and a new way, we can do nothing but manifest the corruption that is natural to us.