To say that one hopes that something does not happen.(interjection)
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Use "heaven forbid" in a sentence
"“Oh, no — heaven forbid that anyone should go up to the great Killaine, our self-appointed moral conscience, and show her any flaws in her character.”"
""If she isn't disposed to primp at the coming of a man, heaven forbid that I should be the one to start her," thought Mrs. Comstock."