Hello. You forgot to mention that this question is related to the play "Macbeth" written by Shakespeare. It is always important to put all the necessary information, so that your answer is answered.
Answer:
These lines reflect the theme that looks can be deceiving and that envy can be destructive.
Step-by-step explanation:
Macbeth is a play written by Shakespeare and tells the story of how Macbeth usurped Duncan's throne, killing him. Macbeth does this by encouraging his envy for Duncan's power and influence and the strategies of his wife, Lady Macbeth. However, Duncan and Macbeth were friends, which makes Macbeth feel very remorse and guilt for what he did, during some moments of the narrative.
The lines quoted in the question above refer to the moment when Lady Macbeth instructs her husband how to kill Duncan. She asks him to be very friendly and to be sneaky as a charge, attacking Duncan the moment he least expects it. This reflects the theme of how appearances can be deceiving and how envy can be so destructive as to lead a friendship to cruel and frivolous acts.