This point is both a step forward and a step back for Macbeth; his former friend Banquo is dead, removing a source of suspicion, but Banquo's son lives, ready for revenge. The blood Macbeth sees on the murderer's face reflects both his rise to power and his fall from grace. Before this scene, however, Macbeth murders King Duncan. He almost does not go through with it, but for Lady Macbeth convincing him first that he is no man if he does not, and second by outlining how they'll get away with it: "what not put upon / His spongy officers, who shall bear the guilt" (1, 7, 70-1). The word "spongy" refers both to the fact that they are going to get the officers drunk, and that the officer's clothes will soak up the blood from the daggers. In the scene after the murder, Lady Macbeth tells her husband to "wash this filthy witness from your hand" and "smear / the sleepy grooms with blood (II, 2, 44; 46-7). Just as in the later scene with Banquo's murderer, blood marks both a step forward and an immersion into evil; the result of Macbth's ambition is blood. In this same scene, Macbeth reveals that he could not say "Amen" when the guards said "God bless us": "But wherefore could not I pronounce 'Amen'? / I had most need of blessing" (II, 2, 28-9). This inability is a symbol of the evil of which Macbeth is now a...

After Macbeth has become king, many of the other Scottish nobles rise up in rebellion. Lady Macbeth has basically gone insane, sleepwalking and talking distractedly, rubbing her hands and saying "Out, damned spot! out, I say!...who would have though the old / man to have had so much blood in him?" (V, 1, 35). Lady Macbeth cannot wash the imaginary blood from the crimes off her hand; she has descended into madness along with her evil. It was largely her persuasion that drove Macbeth to commit the first bloody murder of Kin Duncan, but he was quick to pick up on the effectiveness of violence, murdering his friend without much thought, only regretting it in his later guilt.
Both Macbeth and Lady Macbeth suffer from a surfeit of ambition, and each step in their path up towards the throne and down towards the bowels of human behavior is accompanied by blood, whether it be real, imagined, or both. Blood is something directly tied to royalty; the issues of heredity were major problems during Shakespeare's day and the Scottish King James' rise to the throne. Perhaps part of the message of this play is not…