You shall not go up and down as a talebearer (rachil) among your people; neither shall you stand idly by the blood of your neighbor: I am Adonai.
(א) לֹ֥א תִשָּׂ֖א שֵׁ֣מַע שָׁ֑וְא אַל־תָּ֤שֶׁת יָֽדְךָ֙ עִם־רָשָׁ֔ע לִהְיֹ֖ת עֵ֥ד חָמָֽס׃ (ס)
(1) You must not carry false rumors; you shall not join hands with the guilty to act as a malicious witness:
(ז) כת מספרי לשון הרע נחלקת לששה חלקים: האחד: מי שהוא אומר רע על בני אדם, שכן עשו לו. ולפעמים יאמר דופי על אדם כשר ונקי – אז הוא משקר וגם מספר לשון הרע. והוזהרנו מן התורה שלא לקבל לשון הרע. ודע: כאשר יודה השומע על לשון הרע – אז הוא כמו מספר, כי כל השומעים שהוא מודה יאמרו: כיון שהוא מודה, אם כן אמת הוא הדבר. ואפילו אם לא יודה אלא שומע ומראה עצמו כמקשיב אל הדברים ומאמין בדברים בפני בני אדם – בזה יאמינו גם אחרים. והוא מסייע למספר לשון הרע, כי אם היה גוער במספר לשון הרע – היה מונע עצמו מלספר לו יותר. אבל עתה שהוא מקשיב ומראה לו פנים – אז גורם לו לדבר יותר. והזהירנו במצוות לא תעשה (שמות כג א): "לא תשא שמע שווא" – שלא נאמין סיפור לשון הרע בלבבנו, להחזיק במחשבותינו שהדברים אמת, ולהבזות בעינינו את מי שנאמרו עליו.
(7) Gossips may be divided into six categories.
The first is the one who speaks evil of people and says, "Thus did they do," when in fact they did not do so, and at times the individual will slander an honorable and innocent person — in which case this person is both a liar and a gossip.
And we have been warned by the Torah not to accept gossip because it may be false, as it is said, "Thou shalt not utter a false report" (Ex. 23:1).
And one who speaks gossip, will also be quick to accept gossip.
And you should know that if one who hears gossip endorses what they have heard, then they are just as guilty as the gossiper.
For all who hear that they agreed, will say, "Since they endorse it, it must be true." And even if they do not agree, but simply listens intently to the words, and appears to believe them, in the presence of people, they cause others to believe them too, and thus they help the gossiper.
For if they were to scold the gossiper, then they might restrain the gossiper from telling more, but since they pay attention and shows that they are interested, they cause the gossiper to speak even more gossip.
And, behold, we have been warned by the verse, "Thou shalt not utter a false report" (Ex. 23:1) that we should not believe a gossip story in our hearts, for this would leave a strong imprint in our thoughts that the words are true and cause us to despise the object of the gossip.
(From a compilation of Jewish ethical teachings. Composed: Middle-Age Germany, c.1400 - c.1500 CE. The work advocates improving one’s character and exercising balance in one’s life.)
Let there be light vs. Sticks and stones...
(3) God said, “Let there be light”; and there was light.
(כא) מָ֣וֶת וְ֭חַיִּים בְּיַד־לָשׁ֑וֹן...
(21) Death and life are in the power of the tongue...
(טו) ואמרו רבותינו זכרונם לברכה (ערכין טו ב): לשון הרע הורגת שלושה בני אדם: האומרו, והמקבלו, ואותו שנאמר עליו. והמקבל לשון הרע על חברו נענש יותר ממי שאומרו. מספרי לשון הרע אסור לדור בשכונתם, כל שכן לישב אצלם לשמוע דבריהם.
(15) And our Sages, of blessed memory, said, "Gossip slays three people — the one who speaks gossip, the one who listens to it and the one about whom the gossip is said" (Arakin 15b).
And the one who listens to the gossip is guiltier than the one who speaks it.
It is forbidden to dwell in the neighborhood of gossips, all the more so is it forbidden to sit with them and listen to their words.
If we agree, gossip is not a good practice, why is it so hard to avoid?
EVIL TALK (LASHON HARA)
The most common, and perhaps the most serious speech problem is lashon hara, literally, "evil talk." It refers to any statement that is derogatory or potentially harmful to others -- even if it is true. Although there are other distinctions in Jewish law, the term lashon hara is also popularly used to include tale bearing (rechilut) and slander (motzei shem ra) or spreading lies.
HURTFUL WORDS (ONA'AT DEVARIM)
Words can cause more pain than any weapon. The Torah says that the greatest pain in this world is embarrassment. One who embarrasses another so the person blushes is judged as if he spilled blood.
DECEPTIVE TALK (GANEVAT DA'AT)
Fooling people with words is also problematic. Asking a salesman "How much is this item?" is deceptive if one has no intention of actually buying the item. In many other ways we mislead others through our speech, including flattery and boasting.
DISGUSTING SPEECH (NIVUL PEH)
Included in this category are such things as curse words, off-color jokes, or negative innuendo. What's wrong with saying an occasional curse word? The Torah teaches that the way one acts on the outside affects who one is on the inside. So even if a person is basically good, once he begins to speak in a crude way, his character will become negatively affected.
Idle chatter also falls into this category of impure speech. A Jew shouldn't talk just for the sake of talking. First, this often leads to gossiping about others, simply because a person has nothing better to say. Second, in Judaism there is a concept that each person is allotted a certain number of words in their lifetime. Who wants to waste them on idle chatter?
-- https://www.aish.com/jl/i/s/kosher_speech.html
Okay, okay...but what about SHMOOZING? Isn't that also a key feature of being Jewish and doing Jewish together? And what about those moments when it's better to lie to protect someone by lying than tell the truth and hurt their feelings?
Yet, for all the high value it attaches to truthfulness, the Jewish tradition is sufficiently realistic to acknowledge that there are occasions when the telling of a “white lie” can be in order; for instance, where the intention is to promote peace and harmony ([Babylonian Talmud] Yevamot85b).
The [Babylonian] Talmud (Bava Metzia 23b-24a) observes that a scholar will never tell a lie except in three instances of “tractate,” purya, and “hospitality.”
The commentators explain “tractate” to mean that a modest scholar is allowed to declare that he is unfamiliar with a tractate of the Mishnah in order not to parade his learning.
Rashi translates purya as “bed” and understands it to mean that if a scholar is asked intimate questions regarding his marital life he need not answer truthfully. The Tosafot [authorities of a certain later school, commenting on Rashi’s comments] find it hard to believe that such questions would be addressed to the scholar or anyone else and they understand purya to be connected with the festival of Purim. If the scholar is asked whether he was drunk on Purim, he is allowed to tell a lie about it.
“Hospitality” is understood to mean that a man who has been treated generously by his host may decide not to tell the truth about his reception if he fears that as a result the host will be embarrassed by unwelcome guests.
--Dr. Louis Jacobs, The Jewish Religion: A Companion
Maybe honesty isn’t always the best policy.
In the Talmud (Ketubot 17A), scholars from the schools of Hillel and Shammai disagree about everything. In one famous story, they debated what words one should sing when dancing in front of a bride at her wedding. The rabbis from Hillel’s school advise dancers to chant the same words in front of every bride: “What a beautiful and graceful bride!” The rabbis from the school of Shammai point out that this could be dishonest: “If she is lame or blind, are you really going to say of her, ‘What a beautiful and graceful bride?’”
Shammai’s scholars take a hard line against lying. Rather, they suggest, each bride should be described “as she is.”
So what’s more important–telling the truth or making others feel good?
Jewish law rules in favor of Hillel–we bend the truth and call even the ugliest bride a beauty. Some situations call for a pretty lie, rather than an ugly truth.
-- https://www.jta.org/jewniverse/2010/is-every-bride-beautiful-2
A Chasidic tale vividly illustrates the danger of improper speech: A person went about the community telling malicious lies about the rabbi. Later, they realized the wrong they had done, and began to feel remorse. They went to the rabbi and begged for forgiveness, saying they would do anything they could to make amends. The rabbi told the person, "Take a feather pillow, cut it open, and scatter the feathers to the winds." The person thought this was a strange request, but it was a simple enough task, and they did it gladly. When they returned to tell the rabbi that they had done it, the rabbi said, "Now, go and gather the feathers. Because you can no more make amends for the damage your words have done than you can recollect the feathers."