For a good tree brings not forth corrupt fruit; neither does a corrupt tree bring forth good fruit.
All Commentaries on Luke 6:43 Go To Luke 6
John Chrysostom
AD 407
But although the fruit is caused by the tree, yet, it brings to us the knowledge of thetree, because the distinctive nature of the tree is made evident by the fruit, as it follows, Forevery tree is know by its fruit.
For it is a natural consequence when wickedness abounds within, that wicked words are breathed as far as the mouth; and therefore when you hear of a man uttering abominable things, do not suppose that there lies only so much wickedness in him as is expressed in his words, but believe the fountain to be more copious than the stream.