Final answer:
In 'Macbeth,' Lady Macbeth believes water can cleanse the guilt of King Duncan's murder, advising Macbeth to wash his hands to remove evidence and guilt.
Step-by-step explanation:
In William Shakespeare's Macbeth, it is Lady Macbeth who believes that a little water can cleanse them of their wrongdoing. After Macbeth murders King Duncan, Lady Macbeth counsels him, saying, "Go get some water, And wash this filthy witness from your hand." She suggests that washing their hands will remove the physical evidence of their crime and symbolically cleanse them of their guilt. This contrasts with her later descent into madness, where she obsessively washes her hands, trying to cleanse herself of the guilt that water can no longer remove.