Whence is that knocking?

  Knock within.
Macbeth
Whence is that knocking?
How is ’t with me when every noise appalls me?
What hands are here! Ha, they pluck out mine eyes.
Will all great Neptune’s ocean wash this blood
Clean from my hand? No, this my hand will rather
The multitudinous seas incarnadine,
Making the green one red.

Will all great Neptune’s ocean wash this blood
Clean from my hand?

  Enter Lady Macbeth.
Lady Macbeth
My hands are of your color, but I shame
To wear a heart so white.
  Knock.
I hear a knocking
At the south entry. Retire we to our chamber.
A little water clears us of this deed.
How easy is it, then! Your constancy
Hath left you unattended.
  Knock.
Hark, more knocking.
Get on your nightgown, lest occasion call us
And show us to be watchers. Be not lost
So poorly in your thoughts.
Macbeth
To know my deed ’twere best not know myself.
  Knock.
Wake Duncan with thy knocking. I would thou couldst.
  They exit.