"With their words, the godless destroy their friends, but knowledge will rescue the righteous."
Proverbs 11:9 (NLT)
The proceeding proverbs are helpful to broaden the whole picture with this verse --
3 The integrity of the upright guides them,
but the unfaithful are destroyed by their duplicity.
4 Wealth is worthless in the day of wrath,
but righteousness delivers from death.
5 The righteousness of the blameless makes their paths straight,
but the wicked are brought down by their own wickedness.
6 The righteousness of the upright delivers them,
but the unfaithful are trapped by evil desires.
7 Hopes placed in mortals die with them;
all the promise of their power comes to nothing.
8 The righteous person is rescued from trouble,
and it falls on the wicked instead.
9 With their mouths the godless destroy their neighbors,
but through knowledge the righteous escape.
Verse 8 helps I think. Very often those trying to harm others with words and tricks will themselves fall into a snare, often of their own making. The trap they think to set for others destroys them instead (the book of Esther illustrates this strongly).
Paraphrasing verse 9 -- the malicious gossip or slanderer seeks to harm others by saying untrue or exaggerated descriptions, or half-truths meant to create an illusion. But if the person being slandered is righteous, this attack will not work in the end.
Ellicott says: "Through knowledge.--The just, by the knowledge given them by God, shall see through the fraud."
Proverbs 11:9 With his mouth the ungodly man destroys his neighbor, but through knowledge the righteous are rescued.