A little water clears us of this deed.

– William Shakespeare

Macbeth, Act 2, Scene 2. Lady Macbeth believes that her guilt for her part in the murder of King Duncan will be cleansed by simply washing her hands. While it may wash away the evidence, she will be unable to erase the guilt. Here we have an example of proleptic irony, foreshadowing her inability to wash her hands clean of the guilt of Duncan’s blood in Act 5.