Final answer:
Lady Macbeth wants Macbeth to abandon his ambitions.
Step-by-step explanation:
Lady Macbeth says, "You must leave this" in line 39. In this context, she means that Macbeth needs to abandon his ambitions. She is urging him to give up his desire for power and control. Lady Macbeth recognizes the negative consequences of their actions and believes that it is necessary for Macbeth to let go of his ambition in order to maintain a sense of morality and peace.