One spooky Halloween saying from William Shakespeare's "Macbeth" is, "Double, double toil and trouble, Fire burn and cauldron bubble." Three witches speak these lines while gathered around a cauldron in a cave.
Another eerie saying from a Shakespeare play is this one from "Hamlet," "Tis now the very witching time of night, When churchyards yawn and hell itself breathes out Contagion to this world." Hamlet explains in the play that the dead of night is the time when evil is free to roam the world.
A more modern example of a spooky Halloween saying is this one from Dexter Kozen, "Shadows of a thousand years rise again unseen, Voices whisper in the trees, 'Tonight is Halloween!'”