“A good man out of the good treasure of his heart bringeth forth that which is good; and an evil man out of the evil treasure of his heart bringeth forth that which is evil: for of the abundance of the heart his mouth speaketh.”
Luke 6:45 — Greek Interlinear
Church Fathers on Luke 6:45
Our Lord continues the words which He had begun against the hypocrites, saying, For a good tree brings not forth corrupt fruit; i.e. as if He says, If you would have a true and unfeigned righteousness, what you set forth in words make up also in works, for the hypocrite though he pretends to be good is not good, who does evil works; and the innocent though he be blamed, is not therefore evil, who does good works.
But take not these words to thyself as an encouragement to idleness, for the tree is moved conformably to its nature but you have the exercise of free will; and every barren tree has been ordained for some good, but you were created to the good work of virtue.
He does not then exclude repentance, but a continuance in evil, which as long as it is evil cannot bring forth good fruit, but being converted to virtue, will yield abundance. But what nature is to the tree, our affections are to us. If then a corrupt tree cannot bring forth good fruit, how shall a corrupt heart?