In Act 1 Scene 5 Lady MacBeth speaks to MacBeth. The powerful words she uses encourage him to carry out the plan to murder King Duncan. Her lines are also among the most memorable of the play.
She says to her husband:
Shall sun that morrow see!
Your face, my thane, is as a book where men
May read strange matters. To beguile the time,
Look like the time; bear welcome in your eye,
Your hand, your tongue: look like th'innocent flower,
But be the serpent under't. He that's coming
Must be provided for: and you shall put
This night's great business into my dispatch;
Which shall to all our nights and days to come
Give solely sovereign sway and masterdom."
Lady MacBeth compares King Duncan to the sun. As the sun in the sky rules over all below, King Duncan rules over Scotland. The plan is to murder King Duncan during the night. Once the plan is complete, he will not see morning.
She calls MacBeth a thane because he is not yet king. A thane is a Scottish prince.
She warns her husband that his face could make others suspicious of his intentions. It is like an open book. She wants him to remove any feelings of guilt about the plan.
To fool time, one must look like time. With these words, she reminds her husband that he must look and act the same as always. He must not draw any attention to himself. He must welcome King Duncan as if he were an honoured guest. His looks, actions and words must convince King Duncan that MacBeth is to be trusted. Though he should appear to be an innocent flower, he must be the serpent under it. He must be the exact opposite of what he appears.
The guest who is coming, King Duncan, must be given good care. Lady MacBeth makes it clear that she is the one in charge of the murder. The night's great business shall fall under her control. In the days and nights following the murder, she and her husband, the future queen and king of Scotland, shall have complete control and mastery of the kingdom.
Lady MacBeth's words are critical because she senses her husband's hesitation. To assure him, she tells him that they will soon be the ones in control of the Scottish kingdom. The irony of the play is that Lady MacBeth is later consumed with feelings of guilt and seems to regret her actions. MacBeth, on the other hand, loses his feelings of guilt as he becomes more self-centred and power-hungry.