Rav Hamnuna the Elder said this: "Do not let thy mouth cause thy flesh to sin," (Kohelet, 5:5.) A man should not allow his mouth to utter words that may bring him to lustful thoughts, and thus cause his holy flesh, on which is stamped the holy Brit, to sin. For whoever does this is dragged into Gehinom. The one presiding over Gehinom is called Duma, and there are tens of thousands of angels of destruction with him. He stands at the door of Gehinom. But all of those who have guarded the holy covenant of the Brit in this world, he is impotent to harm them.