Double, double toil and trouble; Fire burn and cauldron bubble.

This couplet is chanted by the three Weird Sisters (witches) in William Shakespeare’s tragedy Macbeth during their spell-casting scene around a boiling cauldron. It occurs in Act 4, Scene 1, as they prepare a prophetic apparition for Macbeth, who has returned to them seeking reassurance after seizing the Scottish crown. The witches’ ritual—mixing grotesque ingredients and repeating incantatory refrains—creates an atmosphere of dread and moral inversion, underscoring the play’s fascination with equivocation, temptation, and the supernatural’s role in political violence. The refrain punctuates the scene like a chorus, heightening theatrical rhythm and menace.

The lines function as an incantation: their heavy alliteration, internal rhyme, and pounding trochaic meter (often associated with the witches) produce a hypnotic, ritualistic sound. “Double” suggests intensification—trouble compounded, evil amplified—while the boiling “cauldron” evokes a world in which natural order is perverted and destructive forces are being deliberately brewed. Dramatically, the refrain signals that Macbeth’s fate is being shaped through deception and half-truths: the witches’ “fire” and “bubble” are not merely stage spectacle but a metaphor for the volatile mixture of ambition, fear, and moral corruption that will erupt into further bloodshed.

“Double, double toil and trouble; / Fire burn, and cauldron bubble.”