Luke 6:45
A good man brings good things out of the good stored up in his heart, and an evil man brings evil things out of the evil stored up in his heart. For the mouth speaks what the heart is full of — the good treasure/evil treasure distinction is the application of the tree/fruit principle to the human person. The mouth speaks what the heart is full of: speech is the most reliable indicator of inner character. What overflows in words reveals what fills the heart.