מוסר אויף ישעיהו 9:16

And behold this group of slanderers is divided into six sections:
And the first section: When he attributes a blemish to a person and [that person] does not have the blemish. There are times that he will lie against beauty. And behold the heart of this one (has his mouth jump the trait of) [gathers the evil of the traits of] two bad groups - which are the group of the liers and the group of the slanderers. And behold we have been warned by the Torah not to accept evil speech - perhaps it is empty or a false matter - as it is stated (Exodus 23:1), “You must not carry false rumors.” And King Solomon, peace be upon him, said (Proverbs 17:4), “An evildoer listens to bad talk; a lie gives ear to malicious words.” Its explanation is - two groups accept evil speech: The first is is a violent evildoing man - from the usage [in] (Isaiah 9:16), “for all are ungodly and doing evil” - for he suspects the innocent, and loves to find a blemish and guilt about his fellow and a disgrace to his honor. And it will be that when he hears someone saying evil speech about his companion, the violence in his heart brings him to believe that the things are true. And the second group is [that of] the lying man. He also listens and believes malicious talk. Since he does not distance himself from false words, he will not be concerned if he accepts a lie, or if he listens to a false rumor. Hence he will be quick to accept evil speech. [The meaning of] “a lie gives ear,” is like a man of lies. And likewise (Jeremiah 9:5), “You dwell in the midst of deceit,” [means] in the midst of people of deceit; [and also] (Psalms 109:4), “and I am prayer,” [means] a man of prayer.

And the fifth section: Vulgar speech. Our Rabbis, may their memory be blessed, said (Shabbat 33a), “Anyone who speaks vulgarly - even if he was sealed for a decree of seventy years of good, it will be reversed to bad.” And Isaiah said (Isaiah 9:16), “That is why my Lord will not spare their youths, nor show compassion to their orphans and widows; for all are ungodly and wicked, and every mouth speaks vulgarity.” And on account of this, one who speaks vulgarly has a heavy iniquity and is ungodly and wicked. For he has abandoned and left shame and modesty, which are the famous traits of the holy seed (of Israel); and went to the paths of brazenness - which is the trait of the evil boors. Secondly - because he has profanced the Holy One of Israel, as it is stated (Deuteronomy 4:6), “and they will say, ‘Surely, that great nation is a wise and discerning people.’” But this one acted like the disgusting foolish ones that are distanced from the ways of the intellect, which is completely beautiful and also pleasant. And their foulness rises and their stink goes up, so every sage and understanding person surely despises and surely abominates them. And behold, he is profaning the tool of the intellect which is more precious than any beloved tool - as it is stated (Proverbs 20:15), “but wise speech is a precious tool.” And the punishment of one who listens to vulgar speech is great, since he does not seal his ear and does not separate from the words of vulgarity. And about him is it said (Proverbs 22:14), “The mouth of a forbidden woman is a deep pit; [He who is doomed by the Lord falls into it].”

They further said (Shabbat 33a): "Due to the sin of obscene speech, new troubles arise and the young men of Israel die" (Isaiah 9:16)