Final answer:
The lines are spoken by Macbeth in Act 3, Scene 1 of Shakespeare's 'Macbeth'. They reveal his insecurity after becoming king and his fear of Banquo.
Step-by-step explanation:
The lines 'To be thus is nothing, but to be safely thus. Our fears in Banquo stick deep' are spoken by Macbeth himself, in Act 3, Scene 1 of William Shakespeare's 'Macbeth'. These lines are important as they reveal Macbeth's growing insecurity and paranoia after becoming king. He fears that Banquo, his once close friend, could jeopardize his position because Banquo's sons are prophesied to be kings. This means Banquo could potentially have a reason to overthrow Macbeth.
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