1 Peter‬ ‭3‬:‭10 (click for details)

GUILE, noun gile. Craft; cunning; artifice; duplicity; deceit

EVIL 

2556 kakós (an adjective, and the root of 2549/kakía, "inner malice") – properly, inwardly foul, rotten (poisoned); (figuratively) inner maliceflowing out of a morally-rotten character (= the "rot is already in the wood").

The word evil here refers to all types of evil that can be spoken.  A positive way to say this is found in Ephesians 4:29

Let no corrupt communication proceed out of your mouth, but that which is good to the use of edifying, that it may minister grace unto the hearers.

We fool ourselves into thinking it is ok to talk about someone judgmentally, if the thing we are saying is ‘true.’  The truth is, unless we are saying that thing to build up the person, or to try to help in the situation, we are truly just telling it to delight ourselves in gossip.  We edify ourselves in effect stating how much better we are than the person we are talking about.  We also put ourselves in the position of God, presuming we know what someone’s motives are, when in truth, we don’t know why we do some of the things we ourselves do.

For what man knoweth the things of a man, save the spirit of man which is in him? even so the things of God knoweth no man, but the Spirit of God.  1 Corinthians 2:11

Make no mistake, we will answer for every word spoken, every hurt caused by our tongue, and will be judged as we have judged.  Remember, Jesus is in the business of forgiveness and of building up our weak faith and lives.  Satan is in the business of destroying.

The thief cometh not, but for to steal, and to kill, and to destroy: I am come that they might have life, and that they might have it more abundantly. John 10:10

If someone has truly done wrong, don’t worry, God will judge.  They will not escape his judgement.  But if we engage our tongues, then we give God cause to judge us as well.

“A good man out of the good treasure of the heart bringeth forth good things: and an evil man out of the evil treasure bringeth forth evil things. 36 But I say unto you, That every idle word that men shall speak, they shall give account thereof in the day of judgment. 37 For by thy words thou shalt be justified, and by thy words thou shalt be condemned.  Matthew 12:35-37”

“ let him refrain his tongue from evil;

bridle that unruly member, which has a world of iniquity in it; let him keep it as with a bit, from the vices incident to it; from all obscene words, filthy and corrupt communication, whatever is unsavoury and unedifying; from lying, cursing, swearing, and particularly from railing and evil speaking, in return for such language, which is chiefly meant; as well as from belching out blasphemies against God, and damnable heresies among men; for whoever would be thought a religious man, and lays no restraint on his tongue, his religion is a vain thing, ( James 1:26) “. John Gill’s commentary