Proverbs 26:18

As a mad man who casteth firebrands, arrows, and death,

Together with the following verse, the verse likens one who deceives a neighbor and then pleads it was only a joke to a madman casting firebrands, arrows and death. The likeness teaches that deceit veiled as humor does real and serious harm even when the speaker disclaims serious intent. That warning reaches to exaggeration, to misrepresentation in trade, and to other forms of dishonest speech.

The verse also describes a gossiping and malicious tongue as recklessly scattering harm like incendiary weapons. Such talk wounds innocent people and destroys their hope and courage. It indulges in exposing what is objectionable in others without caring for the damage done, striking those already burdened with trouble. It ruins a person's reputation and usefulness.