LADY MACBETH
Out, damned spot! out, I say!—One: two: why,
Then, 'tis time to do't.—Hell is murky!—Fie, my
Lord, fie! a soldier, and afeard? What need we
Fear who knows it, when none can call our power to
Account?—Yet who would have thought the old man
To have had so much blood in him.
DOCTOR
Do you mark that?
LADY MACBETH
The thane of Fife had a wife: where is she now?—
What, will these hands ne'er be clean?—No more o'
That, my lord, no more o' that: you mar all with
This starting.
A reference to Lady MacDuff, who was murdered along with her son in  Act 4, Scene 2 . The opening rhyme of the line, almost a sing-song, gives way to questioning. Similarly, Lady Macbeth’s early confidence has given way to her current doubt and guilt.
Out Damned Spot