Macbeth is worried about hearing a voice saying does murder sleep what Lady then tell him to do?

Lady Macbeth tells Macbeth to ignore the voice and focus on the task at hand. She says, "These things must not be thought / After these ways: so, it will make us mad." She then encourages him to go and kill Duncan, saying, "Screw your courage to the sticking-place, / And we'll not fail."