לֹא־תֵלֵ֤ךְ רָכִיל֙ בְּעַמֶּ֔יךָ לֹ֥א תַעֲמֹ֖ד עַל־דַּ֣ם רֵעֶ֑ךָ אֲנִ֖י יְהוָֽה׃
너는 네 백성 중으로 돌아다니며 사람을 논단하지 말며 네 이웃을 대적하여 죽을 지경에 이르게 하지 말라 나는 여호와니라
Chofetz Chaim
It is forbidden to speak demeaningly of one's friend, even if it be absolute truth. And this is termed everywhere by Chazal "lashon hara." (For if there were in his words an admixture of falsehood, by which his friend is demeaned even more, this is in the category of "motzi shem ra" [spreading a false report], in which his sin is far greater). And the speaker [of lashon hara] transgresses a negative commandment, viz. (Vayikra 19:16): "Do not go talebearing among your people." And this [lashon hara] is also in the category of rechiluth.
Chofetz Chaim
One who bears tales about his friend transgresses the negative commandment of (Vayikra 19:16): "You shall not go talebearing among your people." It is a great sin and leads to the killing of many souls in Israel, for which reason it is followed by "You shall not stand by the blood of your neighbor." (viz. Rambam, Hilchoth Deoth 8). Go and see what resulted from the rechiluth of Doeg the Edomite [viz. I Samuel 21], because of which there was wiped out the entire city of Nov, the city of Cohanim. And this negative commandment which we have adduced is that which the Torah wrote explicitly for this issur. But aside from this, there are many other [relevant] negative and positive commandments, as explained above in the introduction.
Chofetz Chaim
In the Blessed One's love for His people Israel and His great desire for their good — to the point of calling them "sons," and "the portion of the L–rd," and "inheritance," along with many other terms of affection which show His great love for Israel, viz. (Malachi 1:2): "I have loved You, said the L–rd, etc.," He distanced them from all forms of evil, especially from lashon hara and rechiluth. For it is these which bring men to quarrels and contention and which very often can lead to the spilling of blood, as the Rambam wrote (Hilchoth Deoth 4:1): "Even though there are no malkoth [stripes] for transgression of this negative commandment, it is a great sin, which leads to the killing of many souls in Israel, for which reason it [i.e., 'Do not go tale bearing among your people' (Vayikra 19:16) is followed by: 'Do not stand (idly) by the blood of your brother' — as evidenced by [the episode of] Doeg Ha'adomi and Nov, the city of priests (viz. I Samuel 22:9)."