Duncan is in his grave;
After life’s fitful fever he sleeps well:
Treason has done his worst; nor steel, nor poison,
Malice domestic, foreign levy, nothing,
Can touch him further.
– William Shakespeare
Macbeth, Act 3, Scene 2. Macbeth is filled with envy of the dead Duncan, who sleeps well and is no longer troubled by life. A number of metaphors compare life to a disease full of struggle, and death to peaceful sleep.