In Macbeth’s speech, “to be thus is nothing,” he uses anaphora and repetition.
Anaphora is the process of referring back to something, and using a word to refer to another. In this case, the word “thus” refers to Macbeth’s kingship. He is basically saying that to be king is nothing, unless he is safely king.
To be thus is nothing,
But to be safely thus. Our fears in Banquo
Stick deep, and in his royalty of nature
Reigns that which would be fear'd. ’ (Act 3, Scene 1)
Macbeth is worried that Banquo is going to interfere, either because he is suspicious or because of the prophecy that his sons would be kings. As a result, even though Macbeth is king, he does not feel comfortable. He is essentially saying: To be king is nothing, unless I can stay king.
There is also repetition here, because the word "thus" is repeated, emphasizing the anaphora.
The use of anaphora in this speech is another way for Macbeth to distance himself from what he is really doing. He is not being a king here, he is being a coward. He cannot even bring himself to say the word “king.”