Proverbs 11:9-13 contain five contrasts, primarily concerned with the intention of wicked people to destroy others by speaking evil against them.
Verse 9: "With their mouths the godless would destroy their neighbors,
but by knowledge the righteous are delivered."
Verse 10: "When it goes well with the righteous, the city rejoices;
and when the wicked perish, there is jubilation."
Verse 11: "By the blessing of the upright a city is exalted,
but it is overthrown by the mouth of the wicked."
Verse 12: "Whoever belittles another lacks sense,
but an intelligent person remains silent."
Verse 13: "A gossip goes about telling secrets,
but one who is trustworthy in spirit keeps a confidence."
What practical lessons can one learn about God and the godly life from these maxims?
1. Wicked people try to destroy others by speaking evil about them. In his commentary on Proverbs in the Daily Study Bible Series, Kenneth T. Aitken writes: "The Whisperer . . . [is known] better under other names: slanderer, gossip, talebearer and the like. At his worst, the whisperer trades in slander. He thinks nothing about inventing and spreading lies about another person out of sheer spite. So the whisperer and the "perverse man" . . . are close companions (16:28). More often than not, however, the whisperer is in the more "respectable" (!) business of gossip. Naturally HE would never dream of telling a lie. So he trades in innuendoes, half-truths, and facts distorted and exaggerated beyond recognition, and spreads them for no better reason than that it makes him feel knowledgeable and important (cf. 11:12). But whether as slanderer, talebearer or gossip, the whisperer is in the business of poisoning relationships (16:28), creating strife (26:20), betraying friends and neighbours (11:13), and also assassination--the ruining of reputations and lives (cf. 11:9; Lev. 19:16)." (page 137).
2. "The blessing of the upright" mentioned in verse 11 apparently is the blessing that the upright is to others [evidently in his speech of encouragement and support and affirmation to others, and perhaps also good things he/she does for others], as the contrast to "the mouth of the wicked" in line b suggests.
3. Verse 12 teaches that it is wise ["intelligent"] to say nothing at all about others than to speak and "belittle" them, that is, say things about them to try to make them appear insignificant to others or to make them feel inferior within themselves.
4. Proverbs 11:9-13 contain basically the same message as Ephesians 4:17-5:16 with its strong emphasis on the power of speech in dealing with others.