Hafetz Haim Halachot
Halacha 9 / 215

Hilchos Lashon Hara, Opening – Negative commands (1)

Whoever speaks against another person breaks a negative commandment, as it says (Vayikra 19:16), "Do not go as a talebearer (rachil) in your nation."

What is a rachil? Someone who carries stories from one person to another, saying, "So-and-so said this about you," or "I heard that so-and-so did this to you" - even if it is true. Such a person is one of those who destroy the world.

There is a much worse sin than this: lashon hara, which is also included in this negative commandment. Lashon hara means saying bad things about another person, even if they are true. Someone who says lies about another person is called a "motzi shem ra" - a slanderer.