Knocking is a motif throughout Macbeth. After Macbeth and his wife complete their hideous murder, they hear a knock within that causes them to immediately fear and begins their slow descent into guilty madness. The Porter imagines Hell's Gate and unwittingly invokes two symbols. First, Macbeth's castle begins to resemble hell as he has committed a hideous crime. Second, the Porter reminds the audience that bad deeds, such as murder and suicide, are met with punishment in hell. This foreshadows not only Macbeth and Lady Macbeth's coming end, but the promise of punishment in the afterlife for their ambition. It is unclear whether or not this line was the basis for the modern Knock, Knock joke.

Donalbain recalls how his father was welcomed into the castle with false smiles and reaffirms his suspicion of Macbeth as the culprit by saying that the closer someone is to you in a blood relationship, the more likely he or she is to kill you. Since Macbeth is the nearest relative of the two princes, Donalbain considers him their greatest threat.

Malcolm agrees with his brother and says that their sorrow can wait until they have fled somewhere safe. Their lack of tears or strong emotions show how fear has a stronger hold over them instead of grief and help to create a sense of fearful urgency on the stage surrounding the two princes.

An auger is a sharp tool primarily used for making holes. In this context, Donalbain means a small, unnoticeable hole. He tells his brother that fate (a violent death) could be waiting for them in any corner of Macbeth's home and that they should flee.

Lady Macbeth's fainting spell in this moment signifies one of two possible interpretations: First, her husband's description of the murdered king possibly makes her recall the image of the dead man so vividly that she faints, revealing herself to be physically weaker than others. Second, Lady Macbeth may be pretending to faint in order to draw attention from her husband, who is running the risk of talking too much and arousing suspicion.

In other words, the reason that tells us to wait for a moment and not act too hastily. Macbeth says his love for Duncan was so strong that he killed the grooms in a moment of passion. Consider how this explanation of why he killed the grooms compares to Macduff's nonviolent reaction to seeing Duncan's body.

Compare this short speech with Macbeth's earlier one in lines 99-104. Whereas earlier he appeared genuine, here the word choice and poor imagery help to illustrate Macbeth's hypocrisy.

While readers know that Macbeth killed the grooms to cover his own tracks, note how Macduff assumes an oppositional attitude with this question. This challenge demonstrates how Macduff might be considering the possibility that Macbeth is guilty of the crime.

These words contain a subtle accusation: Banquo tells Lady Macbeth that her response is not appropriate because she should be more worried about the dead king rather than how it would affect her reputation. He also has reason to suspect that Macbeth committed the crime since he is aware of the witches' prophesies.

Macbeth's beautiful speech shouldn't be regarded as hypocrisy or as a lie. Recall how he did express his remorse after killing Duncan, and in this moment he takes an opportunity to vocalize his feelings, knowing that his full meaning will not be understood by those around him.

Macduff momentarily restrains himself from sharing the news with Lady Macbeth because he considers the news so horrible that it would kill her. However, this moment of consideration for his hostess is quickly abandoned with the arrival of Banquo, to whom Macduff quickly tells the news.

Macduff compares the murder of Duncan to a picture of Judgment Day ("the great doom's image"). He calls everyone in the castle to rise up—as the dead would on Judgment Day—to witness the horror. Note how his speech is broken and truncated in this passage to emphasize his extremely agitated state.

Most likely what Shakespeare intended by the word countenance (to show or express) was that the people Macduff summons will appear in their nightgowns and therefore resemble ghosts, a sight that will "countenance" the horror of the King's murder. Shakespeare realized that if all the sleepers are summoned so urgently in the wee hours of the morning, they would have to appear in their nightgowns; therefore, he makes the most of the spectacle.

In Greek mythology, Gorgons were monsters who could turn anyone who looked at them into stone. The most famous gorgon was Medusa. Macduff uses this phrase to say that the sight of the murdered king is as terrible and destructive as seeing a Gorgon would be.

The word physics when used as a verb means to remedy or treat with medicine. In this context, Macbeth says that hosting the king is an honor and a privilege that fixes all pains.

Notice how awkward and stilted Macbeth's questions are. This is not only further evidence of how unprepared Macbeth was to be in this situation, but it is also evidence that Macduff will recall later.

Macduff is referring to Duncan's body. Since kings were thought to be divinely appointed, then their bodies would be considered holy and sacred.

Even though they're talking about the weather, Macbeth's statement here is a perfect example of understatement. For him, the weather is of little concern considering the kind of "rough night" Macbeth has just had.

By "obscure bird," Lennox means an owl hooting in the night. Recall that the owl is considered an omen of death and that Lady Macbeth also heard the owl shriek while her husband murdered Duncan.

One edition of Macbeth defines "limited service" as "appointed duty." Macduff is probably furious at having to wait so long to be let into the castle, but he is controlling his temper. Here he reminds Macbeth that he was knocking at the gate so persistently because he is obeying a royal command.

Notice how short Macbeth's replies are to Macduff's questions. Considering his lack of sleep and the guilt weighing on his conscious, this manner of speaking comes across as a little too brief and inappropriate for speaking with a fellow Thane. Macduff will remember this behavior later in the play.

The Porter makes a pun here. The word lie, as in "lie down," sounds the same as the word lye which means "urine." The humor is in the idea that too much drink makes someone fall asleep and possibly wet themselves.

In a scene meant for comic relief, the Porter tells Macduff how too much alcohol has deceptive effects on people. Following this line, he uses contrasting expressions to make a joke to the audience about how drink can make a man sexually aroused but leave him unable to physically perform.

Macduff is the Thane of Fife, a nobleman of Scotland. Interestingly, his knocking at Macbeth's gate indicates that he was spending the night camped outside the castle walls. This implies that Duncan was traveling with a much larger contingent of troops and nobleman.

Presumably, the Porter has made his way to the gate and decided to stop playing his game of imagining himself as a porter of the gate to hell.

Continuing with his hell-gate fantasy, the Porter imagines the next person he would encounter. In this case, Shakespeare alludes to the Gunpowder Plot of 1605 in English history, when conspirators sought to overthrow the British monarchy. The “equivocator” likely alludes to a Jesuit priest named Father Henry Garnet, known as the great "equivocator" because of his ability to use unclear language to deceive others. He was eventually hanged for his role in the event.

Beelzebub is a high-ranking fallen angel who served Satan in Milton's Paradise Lost. In common usage, the name Beelzebub can be used synonymously or as a nickname for the Devil or Satan.

The Porter, likely still drunk, is imagining what being the gatekeeper of hell would be like and who he would meet. He imagines encountering a farmer who stockpiled his crops to sell at inflated rates during the next famine and then hanged himself when the famine never came. This imaginary farmer represents the sins of greed and suicide, which the Porter thinks would make him a perfect candidate to meet in hell.

As Macbeth and his wife leave the courtyard, the scene doesn't change. The porter, slowly wakened by the knocking from his drunken sleep, makes his way to the door. His speech helps move the time along as Macbeth cleans his hands and tries to pretend that he was asleep while Duncan was murdered.

Lennox is only present to give Macbeth someone to talk to while he is standing outside Duncan's chamber waiting for Macduff's outcry when he discovers the king's murdered body. Macbeth's tension while he waits would not come across effectively if he were all alone. With Lennox present, Macbeth can speak short lines which betray his guilt and fear much better than is he were just standing there alone. There must seem to be a long passage of time before Macduff's expected outburst is heard. The audience knows it is coming and shares Macbeth's horrified anticipation. Lennox is a young man. His youth and innocence are intended to contrast with Macbeth's guilt. Macbeth is strangely silent because he can't think of anything to say. Lennox does what people generally do to make conversation: he talks about the weather. 

The fact that Macduff had to sleep outside Macbeth's castle suggests that most of the soldiers must have been encamped outside as well. That would mean that Duncan had no armed men to protect him and that he had been at Macbeth's mercy throughout that fateful night. 

One of the meanings of this word is to move or cause someone or something to move after being still. This would likely evoke a strong reaction in Macbeth because it suggests to him that Duncan might not be dead but could be struggling to rise all covered with blood to call for help and accuse his murderer.

It has been suggested that this exchange between Macduff and the Porter was inserted for comic relief.

These words prove that most of the characters were dressed in their nightgowns with only Macduff and Lennox fully dressed. The other nobles have rushed to the courtyard at the sound of the alarm bell. Banquo tells them to dress properly and then attend to the matter at hand.

This is certainly an understatement. The weather outside the castle was rough, but what was going on inside the castle was a whole lot rougher.

Lennox, a young man, is stuck with the grim and unresponsive Macbeth while Macduff goes inside the King's chamber. Like most of us when we have to try to make conversation, Lennox talks about the weather for the entire eight lines. Macbeth can only respond, "'Twas a rough night." Shakespeare makes Lennox an ingenuous, inexperienced young man to serve as contrast to the guilt-ridden, world-weary, aging Macbeth. 

Macduff thinks Macbeth is being cold and angry because he woke him up with his knocking. This line about "a joyful trouble to you" is dripping with sarcasm. Macduff is also daring Macbeth to complain about having to open his gate for a man on the King's business. However, his sarcasm is wasted on Macbeth because the man is almost in a trance, consumed with mixed emotions.

Although the stage directions do not say so, the knocking must be growing louder and more prolonged. We do not know who is knocking as yet, but the knocker must be growing more and more furious and insistent. Macbeth cannot continue to pretend to be asleep with all this racket. 

Macduff is a proud man. He is in an extremely bad mood. He is cold and wet and hasn't slept all night. He doesn't like to apologize for his knocking, since he is on the king's business and there should have been some sober person to open the gate a long time ago. But he does offer a veiled apology here. He is saying, in effect, "I'm sorry to wake you up. I'm tired too." But Macbeth is preoccupied with his own guilt and dread and doesn't even hear what Macduff is saying. Instead of making a courteous reply, Macbeth simply says, "I'll bring you to him." Macbeth is not a real villain and does not know how to act in this situation. Macduff will surely remember Macbeth's strange behavior later on.

Macbeth is frozen with guilt, dread, and remorse. He hasn't slept all night and may never sleep again. His curt replies anger Macduff and will later make him suspicious when he reflects on Macbeth's strange behavior. Macduff thinks Macbeth is angry because of being awakened by his loud and persistent knocking.

Macbeth and his wife had planned to be pretending to be asleep when Duncan's body would be discovered in the morning. But Shakespeare wanted Macbeth to be present at that terrible scene. He also wanted Macduff to be the discoverer because he had to introduce him to the audience and had to show Macbeth and Macduff, protagonist and antagonist, together at least one time before their death duel in the last act. The prolonged knocking at the gate forces Macbeth to come down in his nightshirt to see why no one is responding. He arrives just as the Porter is opening the gate and explaining to Macduff that servants and guards were all dead drunk. Macbeth would probably be in his nightgown, both because he had little time to get dressed and also because he would at least try to give the impression that had been asleep in bed. Macduff naturally assumes his knocking has wakened Macbeth because it is three o'clock in the morning and Macbeth is wearing a nightgown. 

In a scene of comic relief, the Porter hears knocking at the gate and imagines that he is the porter at the gates to Hell. Comic relief allows the release of emotional tensions due to serious or tragic elements in a drama. The Porter's drunken state and conversation about impotency add to the humorous nature of this scene. 

Macduff is stating that the sight of Duncan's murdered body will force those who look upon it to wish they had not seen it. The sight of Duncan's body will hold the men fast (stuck) as if they were turned to stone (analogy to mythology and Medusa). 

This description of a "fevered" earth personifies it, describing it as sick and shaking with the unnatural death of Duncan.

Macduff has been standing out in the cold, rain and wind pounding at the gate. His first words to the Porter are surprisingly mild considering how angry and frustrated he must be. No doubt he does not want to frighten the fellow because he wants to get some information out of him. Macduff has understandably become very suspicious about what is taking so long to open the gate.