from Divrei Hokhmah
THE TONGUE CAN KILL
“The talk about a third [person] kills three persons: him who tells it, him who accepts it, and him about whom it is told….Just as the hand can kill, so can the tongue.” (Talmud Arachin 15b)
The Talmud teaches about the seriousness of lashon hara, speaking negatively about someone. Negative talk hurts the person who tells it, the person who listens to it, and the person who is the subject of such talk. According to our sages, using the tongue in spreading gossip is the same as killing.