“The Prince of Cumberland that is a step on which I must fall down, or else o’erleap, For in my way of lies. Stars, hide your fires, Let not light see my black and deep desires, The eye wink at the end. Yet let that be, Which the eye fears when it is done to see.”

Macbeth is saying at first that to become king, he must kill The Prince of Cumberland (Duncans heir). He then moves onto saying that he doesn’t want heaven/God to see what he is about to do (him killing the Prince of Cumberland and Duncan). He metaphorically says that he should cover his eyes from looking at King Duncan and The Prince of Cumberland being killed with his own bare hands because deep inside he knows that he’s doing morally wrong.