Nothing in his life
became him like the leaving of it.
(1.4.7-8)

Act 1, scene 4 is a continuation of the battle scene of Act 1, scene 2. Sandwiched in between is Macbeth's first encounter with the witches and their prophecy that he will be Thane of Cawdor. In scene 2, King Duncan has ordered Cawdor's execution, and here in scene 4, Malcolm, Duncan's son reports on how the execution went. For the Jacobeans who frequently witnessed executions by beheading, the prisoner pledging loyalty at the last minute was frequently rewarded with pardon. Cawdor, however, does not survive, in spite of confessing 'his treasons', imploring the King's 'pardon', and showing 'a deep repentance'.

...the milk of human kindness.
(1.5.15)

As Lady Macbeth waits for her husband to arrive home after she has received his letter with the news of his promotion and the prophecies, she decides that her husband will be king only through her iron determination since he is sometime too full of compassion, a very unmanly trait. The phrase is therefore at the top of Lady Macbeth's insult list so that when we use the phrase to approve of someone's compassion, we are changing it from an insult to a compliment.

The be-all and the end-all
(1.7.5)

According to the OED, Shakespeare invented this phrase and all subsequent uses by other authors are borrowed from the playwright. In the play, Macbeth is debating with himself about committing the murder of Duncan and becoming king without getting caught. If killing the King would have no consequences, he would have no other problems. But Macbeth knows regicide can never be so simple. For us, it means an event or person that is the beginning and end of all things in one package; an ego maniac; a conceited person.

Knock, knock. Who's there…?
(2.3.5-6)

In one of the very few comedy bits in Macbeth, the Porter is roused to open the gate just after the murder of Duncan. As he goes to the gate half asleep, he engages in a conversation with himself and several others of his own creation. It seems that Shakespeare is responsible for the beginning of the 'Knock Knock' joke. Variety, an entertainment industry magazine, reported on 19 August 1936 that America was caught up in a 'knock-knock craze', and on 14 November 1936, England fell for the tasteless pun answers to the question 'knock-knock' when radio comedian Wee Georgie Wood told several of the jokes on a radio show. Nowadays, the 'knock-knock' joke is an integral part of panto (short for pantomime), a form of interactive theatre that stages children's fairy tales, especially at Christmas in Great Britain.

What's done is done.
(3.2.12)

Here a very calm Lady Macbeth chides her husband for still thinking about Duncan's murder. She tries to tell him that there is nothing that can be done about it: dead is dead. Interestingly this advice to her husband emerges in a negative sentence in her sleep-walking: 'What's done cannot be undone' (5.1.68). Her guilty conscience is even more forceful than the seemingly simple advice she gives Macbeth. Not only can nothing be done about Duncan's murder, but nothing can be done to undo it.

Double, double toil and trouble.
(4.1.10)

Before Macbeth arrives to ask for more prophecy from the witches, they are seen mixing up a potion in a cauldron. This phrase is part of the chant that casts the spell of hard labour and tribulation. In these lines Shakespeare abandons iambic pentameter for tetrameter (four beats per line) which resembles basic song rhythm. With this language and their description as 'unnatural hags', Shakespeare single-handedly created our image of the Halloween witch.

The crack of doom.
(4.1.116)

To the Jacobeans, a 'crack' of thunder announced 'doom' or Doomsday, also known as Judgement Day. In this scene Macbeth has urged the witches to show him more prophecy and when the Apparitions of eight young kings appear in a never-ending line, Macbeth thinks they will 'stretch out to th'crack of doom'; in other words, Banquo's children will be kings for a very long time. This passage would be considered a compliment to James VI of Scotland who, as a Stuart, had recently become King James I of England, taking over from Elizabeth I, the last of the Tudors.

One fell swoop.
(4.3.231)

While we would recognise 'fell' as the past tense of 'fall', Shakespeare's audience would interpret this invented phrase as an extension of Macduff's poultry metaphor when speaking of his wife and children. For the audience, 'fell' meant 'fierce, cruel, or savage' and the word 'swoop' would mean the attack pattern of a bird of prey like the kite in line 219. To Macduff, Macbeth's attack on his family and their murder is like the attack of a kite on defenceless chickens. For us, the phrase means all at once, which is not too similar from Macbeth's murder of Macduff's family.

Out, damned spot.
(5.1.33)

Possibly one of Shakespeare's most famous scenes, the sleep-walking Lady Macbeth speaks out in her dream what she and her husband have done to gain the throne. One of the themes of Macbeth is how difficult it is to wash a sin from the soul, using blood on the hands as a metaphor. The Macbeths learn to their peril that their sins will never be washed away by physical means. This phrase has been used frequently to sell everything from toothpaste to car polish.

The patient must minister to himself.
(5.3.45-46)

A doctor has been summoned to cure Lady Macbeth of sleep-walking, but he tells Macbeth that any cure for the Queen is not within his power. In essence, the doctor is telling Macbeth that guilt will not go away until the guilty party acknowledges the wrong and makes amends, and that Lady Macbeth's walking and talking in her sleep is Macbeth's problem.

Come what may,
Time and the hour runs through the roughest day.
(1.3)

Macbeth mutters this sentence to himself in the scene with the witches. He is confused and bewildered by the witches' prediction that he will become king, but at the end of the scene he comes to believe that he indeed may become king.

All our service
In every point twice done, and then done double
(1.6)

Lady Macbeth's evil cunning is all the more chilling because of her language. Here she welcome's Duncan, whom she has plotted to kill. Her words take on double meaning; she makes hidden references to her plans even as she conceals them.

Away, and mock the time with fairest show:
False face must hide what the false heart doth know.
(1.7)

Macbeth, at Lady Macbeth's urging, finally resolves to murder Duncan. At the conclusion of the scene, he tells Lady Macbeth to leave him, and entertain the guests as if everything is normal.

Go get some water,
And wash this filthy witness from your hand
(2.1)

After the murder of Duncan, Lady Macbeth assists Macbeth in wiping away any traces of the crime. Her "management" of Macbeth and his guilt is one of the characteristics of her behavior throughout the play.

What hands are here? Ha, they pluck out mine eyes!
Will all great Neptune's ocean wash this blood
Clean from my hand?
(2.1)

In the same scene, Macbeth expresses anguish, realizing that nothing will be able to wipe the guilt from his conscience. He proclaims, figuratively, that nothing can wash the blood from his hands, not even all of Neptune's ocean.

Here's the smell of the blood still: all the perfumes of Arabia will not sweeten this little hand. Oh, oh, oh!
(5.1)

As the play progresses, Lady Macbeth deteriorates under the psychological burden of her deeds. Just as Macbeth proclaimed earlier with a similar figure of speech, she realizes that nothing can clear her conscience. Finally, in act V, her guilt becomes too great, and she commits suicide.

Life's but a walking shadow; a poor player,
That struts and frets his hour upon the stage,
And then is heard no more: it is a tale
Told by an idiot, full of sound and fury,
Signifying nothing.
(5.5)

Macbeth's famous words after being told of Lady Macbeth's death; he is filled with anguish, and a expresses a view found in many of Shakespeare's characters, that of life and its seeming futility.