If it were done when ’tis done, then ’twere well
It were done quickly: if the assassination
Could trammel up the consequence, and catch
With his surcease success; that but this blow
Might be the be-all and the end-all here,
But here, upon this bank and shoal of time,
We’ld jump the life to come. But in these cases
We still have judgment here; that we but teach
Bloody instructions, which, being taught, return
To plague the inventor: this even-handed justice
Commends the ingredients of our poison’d chalice
To our own lips. He’s here in double trust;
First, as I am his kinsman and his subject,
Strong both against the deed; then, as his host,
Who should against his murderer shut the door,
Not bear the knife myself. Besides, this Duncan
Hath borne his faculties so meek, hath been
So clear in his great office, that his virtues
Will plead like angels, trumpet-tongued, against
The deep damnation of his taking-off;
And pity, like a naked new-born babe,
Striding the blast, or heaven’s cherubim, horsed
Upon the sightless couriers of the air,
Shall blow the horrid deed in every eye,
That tears shall drown the wind. I have no spur
To prick the sides of my intent, but only
Vaulting ambition, which o’erleaps itself
And falls on the other.

If this business would really be finished when I did the deed, then it would be best to get it over with quickly. If the assassination of the king could work like a net, sweeping up everything and preventing any consequences, then the murder would be the be-all and end-all of the whole affair, and I would gladly put my soul and the afterlife at risk to do it. But for crimes like these there are still punishments in this world. By committing violent crimes we only teach other people to commit violence, and the violence of our students will come back to plague us teachers. Justice, being equal to everyone, forces us to drink from the poisoned cup that we serve to others. The king trusts me in two ways. First of all, I am his kinsman and his subject, so I should always try to protect him. Second, I am his host, so I should be closing the door in his murderer’s face, not trying to murder him myself. Besides, Duncan has been such a humble leader, so free of corruption, that his virtuous legacy will speak for him when he dies, as if angels were playing trumpets against the injustice of his murder. Pity, like an innocent newborn baby, will ride the wind with winged angels on invisible horses through the air to spread news of the horrible deed to everyone everywhere. People will shed a flood of tears that will drown the wind like a horrible downpour of rain. I can’t spur myself to action. The only thing motivating me is ambition, which makes people rush ahead of themselves toward disaster.

Spoken by Lady Macbeth, Macbeth Act 1 Scene 5
The raven himself is hoarse
That croaks the fatal entrance of Duncan
Under my battlements. Come, you spirits
That tend on mortal thoughts, unsex me here,
And fill me from the crown to the toe top-full
Of direst cruelty! make thick my blood;
Stop up the access and passage to remorse,
That no compunctious visitings of nature
Shake my fell purpose, nor keep peace between
The effect and it! Come to my woman’s breasts,
And take my milk for gall, you murdering ministers,
Wherever in your sightless substances
You wait on nature’s mischief! Come, thick night,
And pall thee in the dunnest smoke of hell,
That my keen knife see not the wound it makes,
Nor heaven peep through the blanket of the dark,
To cry ‘Hold, hold!’