Matthew Henry Commentary Proverbs 10:20-21

"The tongue of the righteous is [as] choice silver: The heart of the wicked is little worth. The lips of the righteous feed many; But the foolish die for lack of understanding." — Proverbs 10:20-21 (ASV)

The tongue of the righteous is sincere, freed from the dross of guile and evil design. Godly speech is spiritual food to the needy. Fools die for lack of heart—that is, for lack of thought.