Isidore of Pelusium
Catena Aurea · Lukasevangelium 6
For a good tree bringeth not forth corrupt fruit; neither doth a corrupt tree bring forth good fruit. For every tree is known by his own fruit. For of thorns men do not gather figs, nor of a bramble bush gather they grapes. 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.
(lib. iv. ep. 81.) 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?