Heaven knows what she has known. Lady Macbeth: Here’s the smell of the blood still; all the perfumes of Arabia will not sweeten this little hand. O, O, O. Doctor: What a sigh is there!
Act 2 Scene 1 'Will all great Neptune's ocean wash this blood / Clean from my hand?' Macbeth feels great guilt about murdering Duncan and realises he is never going to get rid of these feelings.