Luke 6:45
A good man out of the good treasure of his heart brings forth that which is good; and an evil man out of the evil treasure of his heart brings forth that which is evil: for of the abundance of the heart his mouth speaks.

Matthew 7:16-18
16. You shall know them by their fruits. Do men gather grapes of thorns, or figs of thistles?
17. Even so every good tree brings forth good fruit; but a corrupt tree brings forth evil fruit.
18. A good tree cannot bring forth evil fruit, neither can a corrupt tree bring forth good fruit.