Albert Barnes Commentary Proverbs 15:7

"The lips of the wise disperse knowledge; But the heart of the foolish [doeth] not so." — Proverbs 15:7 (ASV)

Not so - The word translated “so” is taken by some in its etymological force as “strong,” “firm,” and the passage is rendered “the heart of the fool disperses (supplied from the first clause) what is weak and unsteady,” i.e., “falsehood and unwisdom.” The Septuagint takes it as an adjective, “the heart of the fool is unsteadfast.” The phrase as it stands in the King James Version is, however, of frequent occurrence (Genesis 48:18; Exodus 10:11; Numbers 12:7).