Imagine I give you very expensive wine—very, very expensive wine. I’m holding what’s like a $500 bottle of wine, and I tell you, “Listen, do you want a cup? I want to give you a cup.” And you say, “Yeah.” You go get yourself a dirty cup, a dirty plastic cup that has ashes from cigarettes inside, and then I pour the wine inside. No matter how expensive, awesome, and tasty the wine is, if you pour it into a cup that’s full of ashes, it’s not going to taste good.
Our neshamot (souls) are very expensive, beautiful, powerful, and full of light, and we can grow so much and build so much in this world. But if the tool—the vessel, which is us: our bodies, our speech, our mouth—is full of ashes; if our mouth is dirty with lashon hara; if our mouth is used, chas veshalom (God forbid), to curse, use nivul peh (foul speech), and hurt other people’s feelings; if our tongue is lashon hara, a bad tongue, doing bad things, saying bad things with the mouth, and making fun of other people, then it’s full of ashes. So no matter how beautiful the neshamah is, when it comes out, it’s going to be dirty. The speech is different. The prayer is different. The learning is different. Everything is different.
That’s what the Chafetz Chaim says. You want your Torah to be kadosh and holy? You want your tefillot (prayers) to be holy? One has to stop speaking lashon hara.