Read this passage 
 MACBETH. But in these cases
 We still have judgment here, that we but teach
 Bloody Instructions, which, being taught, return
 To plague th' Inventor: this even-handed justice
 Commends the ingredients of our poisoned chalice
 To our own lips.
 --William Shakespeare, Macbeth, Act I, Scene vil
 Which translation of the passage best explains Macbeth's reasoning for not
 murdering Duncan?