Final answer:
Macbeth reacts to the murderer's statement with guilt and horror, understanding that he has destroyed his own peace and ability to sleep. His feigned ignorance upon hearing of Duncan's murder further reveals his inner turmoil.
Step-by-step explanation:
After Macbeth murders King Duncan, he is confronted by a murderer who tells him that Macbeth has murdered sleep. Specifically, the murderer says, 'Macbeth does murder sleep', the innocent sleep, Sleep that knits up the ravell'd sleeve of care'. Macbeth realizes the gravity of his actions and begins to experience deep guilt and paranoia. His reaction is one of horror and despair, as he understands that he will no longer know the peace that sleep brings. This is evidenced by lines such as 'Macbeth shall sleep no more'. Macbeth's guilt manifests itself in the belief that he has forever destroyed his ability to rest, a fundamental human necessity.
Meanwhile, Macduff discovers the murdered King Duncan and alerts Macbeth and Lennox by exclaiming about the 'most sacrilegious murder'. Macbeth's initial reaction feigns ignorance, asking 'What is 't you say? the life?', pretending not to understand the situation.
Overall, Macbeth's interactions with the murderer and his response to the news of Duncan's death showcase his turmoil and the beginnings of his unraveling as he confronts the ramifications of his gruesome actions.