Matthew 12:34

“But the things that come out of a person’s mouth come from the heart, and these defile them.”

Links spoken words to the heart's condition.

“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.”

Mirrors the idea that words reveal inner character; a parallel passage.

“Above all else, guard your heart, for everything you do flows from it.”

Connects to the idea of guarding the heart, as the source of actions and words.

“By their fruit you will recognize them. Are grapes gathered from thornbushes, or figs from thistles? Likewise, every good tree bears good fruit, but a bad tree bears bad fruit.”

Relates to the analogy of fruit revealing the nature of the tree; words reveal the inner self.

“May these words of my mouth and this meditation of my heart be pleasing in your sight, Lord, my Rock and my Redeemer.”

Addresses the desire to have both words and heart aligned with God.