The pasuk states (Tehillim 120:4): “Sharpened arrows of a mighty man with coals of broom-wood.” Chazal state (Medrash Tehillim Mizmor 120) on this verse: Why is a man’s tongue compared to an arrow? Because there is a difference between an arrow and a sword. If a man unsheathes his sword and is about to kill someone, his victim can beg for mercy and convince him to change his mind and spare his life. However, if a man shoots an arrow at someone, he can no longer change his mind as the act of killing has already been done. Thus, a tongue is like an arrow in the sense that once words have left a man’s mouth, they can never be taken back.
The Medrash continues to say that the reason it is compared to coals is because coals burn for a long time without burning out. It relates a story of two men who sat down to eat by a tree in the desert. They made a fire out of coals they made from the wood of a tree and used it to cook their food. A year later, they returned and found that the coals were still burning under the sand. Lashon hara is compared to coals because its effects are felt for years.
Furthermore, the Medrash says that one who speaks lashon hara kills people with his words, which he shoots out of his mouth like arrows upon unsuspecting victims.
