Musar su Ecclesiaste 10:11

And this is the thing about the group of scoffers - scoffing is divided into four sections:
And the first section is the man of the tongue that spreads the infamy of people, like the matter that is stated (Psalms 50:20), “You are busy maligning your brother, defaming the son of your mother.” And he is called a scoffer, as it is stated (Proverbs 21:24), “The proud, insolent man, scoffer is his name, acts in a frenzy of insolence.” Its explanation is that] two bad traits - which are insolence and pride - gathered and joined in the scoffing man. For without having a benefit from the thing, he causes great damage to his fellows, whose reputations he sullies in the eyes of people. And this is the goal of the scoffer, more than the thief or the extortionist - who does [it] to increase his money. And he is also arrogant - for when one who is lowly and submissive recognizes his own deficiencies and blemishes, he will not scoff at people. And our Rabbis, may their memory be blessed, said (Taanit 8a), “In the future, all the animals will gather together by the snake and say to him, ‘A lion mauls [its prey] and eats; a wolf tears [it] and eats; [but] you, what pleasure do you have [when you bite a person]?’ He will say to them, ‘If the snake bites because no spell was uttered, no advantage is gained by the master of the tongue!’ (Ecclesiastes 10:11).” And this section is also from the sections of the group of the slanderers.

And this is the thing about the group of slanderers:
Our Rabbis, may their memory be blessed, said (Arakhin 15b), “Anyone who speaks evil speech is as though he denied a fundamental principle [of faith] - as it is stated (Psalms 12:5), ‘Who have said, “we will make our tongue mighty; our lips are with us; who is lord over us?”’” Therefore, they considered him as if he denied a fundamental principle. For he causes and brings about great damage and much evil to his fellows by making them foul in the eyes of people or by other ways of [causing them] loss. And it is not likely that a man would prepare a mechanism of destruction and damage that is more bitter than death without it benefitting himself monetarily, unless it is to have his [evil] impulse honor himself and remove the yoke of the Heavens from upon him - to remove ethical constraints - as it is stated in the Psalm, “when the Ziphites came and told Saul, etc., O God, arrogant men have risen against me; a band of ruthless men seek my life; they are not mindful of You.” (This is a scribal error, as there is some difference between the verse brought down by the author, may his memory be blessed, [and his source]. As [in the source], it is written, “For strangers have risen against me, etc.” And the verse that he wrote here is found in Psalms 86:14; but it needs to be corrected and replaced with the verse as it is written there in Psalms 54:5.) And our Rabbis, may their memory be blessed, explained (Midrash Tehillim 54) that they intended that Saul would bless them, as he said to them (I Samuel 23:21), “May you be blessed of the Lord for the compassion you have shown me!” But they did not place God in front of them - as it is written in His Torah (Deuteronomy 27:24), “Cursed be he who strikes down his neighbor in secret.” And it is written (Ecclesiastes 10:11), “no advantage is gained by the master of the tongue!” And it is stated about Doeg (Psalms 52:4-5), “Your tongue devises mischief… You prefer evil to good; the lie, to speaking truthfully. Selah.” And they explained in Midrash Tehillim 52, “What do you benefit and what do you gain when you say evil speech? Is it not that you did not need money, for you had [already] become wealthy - as it is stated about him (I Samuel 21:8), ‘Saul’s chief herdsman.’ It was only because you preferred the evil to the good, and ‘the lie, to speaking truthfully’ - as you have removed His yoke.” And it is stated (Proverbs 6:30), “A thief is not held in contempt for stealing [to fill his hunger]; and it is written after it (Proverbs 6:32), “He who commits adultery is devoid of sense, etc.” This is meaning to say that he is worse than a thief, for [the former] needs to “fill his hunger.” Our Rabbis, may their memory be blessed, said (Midrash Tehillim 120) that one involved in evil speech is worse than both of them. For he does a great sin without benefit, as it is stated (Psalms 120:3), “What can you profit, what can you gain, O deceitful tongue?”

And, more than this, we find in Midrash Aggadath Bereshith 20: "In time to come, all will be healed, but the serpent will not be healed. And just as there is no cure for the serpent, there is no cure in time to come for one who speaks lashon hara against his friend, as it is written (Koheleth 10:11): "If the serpent bites, [it is because] there is no charm [against him]; so, there is no advantage [i.e., cure] for the man of the tongue."