Proverbs 16:21: The wise in heart are called discerning, and pleasant words promote instruction.
True wisdom (godly wisdom) is the subject above. Godly wisdom is recognized by others around you, and they have respect for you because of the decisions you make. We see in the rest of verse twenty-one that people who speak nice things are listened to more readily. People listen and learn more from someone who speaks softly and kindly.
The “sweetness of the lips” is like “words of honey,” which reflect intelligence, judiciousness, and discernment in speech, referring to eloquent discourse from the wise.
Under Gods Command 