The tree must bring forth either good or bad fruit.  These words are still addressed to the Pharisees, who so vehemently opposed Christ’s activities.  He is in the plainest terms asserting that they are bad trees, bringing forth bad fruit.  In verse 34, He castigates them with the same term used by His forerunner, John the Baptist:: “O generation of vipers, how can ye, being evil, speak good things?”  The evil words and blasphemies they had uttered were nothing but symptoms of their corrupt hearts.  They manifested the abundance of putrid corruption which festered in their vile hearts.  A good man will speak good things, to the comfort and edification of the Lord’s people, and the rebuking and warning of those who are out of the way.  An evil man, because every imagination of the thoughts of his heart is only evil continually, will speak evil things, even as these Pharisees had done. 

Our Lord would have us to see that our speech is of utmost importance.  This is attested to in James’ epistle, where we read that the man who is religious, but cannot bridle his tongue, is serving a vain religion.  Even our idle words, Jesus says, must be accounted for at the day of judgment.  I fear that none of us have taken to heart like we should these weighty sayings concerning the use of our tongue.  If we did, a vast percentage of the words we utter would never leave our mouths.  Our speech will, in the end, either justify or condemn our profession of faith.  A true servant of Christ will, in general, be careful to speak good things, for the spiritual benefit of those who hear him.  An evil man will utter only that which is evil and worthless, and of no lasting benefit to anyone.