Will all great Neptune’s ocean wash this blood
Clean from my hand? No, this my hand will rather
The multitudinous seas incarnadine (2.2)

Macbeth speaks this line when he encounters his wife right after murdering Duncan. He refers to both the literal blood on his hand but also to his sense of guilt. He uses grand and dramatic language to imply that the blood could stain all the world’s oceans red. His language implies that the consequences of his action will not be easily hidden, even though his wife implies that blood can be simply washed away. He will forever be a changed man as a result of what he has done. Interestingly, later in the play, Lady Macbeth will also hallucinate that she has blood on her hands and is unable to get them clean, symbolizing her sense of guilt.

Thy bones are marrowless, thy blood is cold
Thou hast no speculation in those eyes (3.4)

Macbeth speaks this line when Banquo’s ghost appears to him at the banquet. Macbeth’s vision of the ghost reveals his guilt over ordering the murder of Banquo and his young son. His sense of guilt is so powerful that he loses his sense of reality and cannot be sure whether he is having a vision or not. He speaks these lines in order to try and reassure himself that Banquo is truly dead. In doing so, Macbeth reveals that his tormented consciousness is leading him to start losing his grip on sanity.

To bed, to bed. There’s knocking at the gate. Come,
come, come, come, give me your hand. What’s done
cannot be undone. To bed, to bed, to bed. (5.1)

Lady Macbeth speaks these lines after she has gone mad. They are the final words she utters in the play, and they reveal how guilt has crushed her strong and assertive personality. She now has to be cared for like a child, and has no plans for the future. No matter how much she repents, the violence and death cannot be undone.