New Revised Standard Version
The mind of the wise makes their speech judicious, and adds persuasiveness to their lips.

Contemporary English Version
You can persuade others if you are wise and speak sensibly.

New American Bible
The heart of the wise makes for eloquent speech, and increases the learning on their lips.

Douay-Rheims Bible
The heart of the wise shall instruct his mouth: and shall add grace to his lips.

The heart of the wise shall instruct his mouth: and shall add grace to his lips.

heart

Proverbs 15:28 The mind of the just studieth obedience: the mouth of the wicked overfloweth with evils.

Proverbs 22:17,18 Incline thy ear, and hear the words of the wise: and apply thy heart to my doctrine: . . .

Psalm 37:30,31 The mouth of the just shall meditate wisdom: and his tongue shall speak judgment. . . .

Psalm 45:1 Unto the end, for them that shall be changed, for the sons of Core, for understanding. A canticle for the Beloved. [2] My heart hath uttered a good word: I speak my works to the king: My tongue is the pen of a scrivener that writeth swiftly.

Matthew 12:34,35 O generation of vipers, how can you speak good things, whereas you are evil? for out of the abundance of the heart the mouth speaketh. . . .

Colossians 3:16 Let the word of Christ dwell in you abundantly: in all wisdom, teaching and admonishing one another in psalms, hymns and spiritual canticles, singing in grace in your hearts to God.