What does the lamb symbolize in "Lamb to the Slaughter"?

The lamb in "Lamb to the Slaughter" symbolizes Mary. Traditionally, in Western culture, a lamb represents the innocent, spotless creature who is killed to atone for another's sin. Christ is often called the lamb of God in Christian theology because he is executed, though completely innocent, to wipe away the sins of humankind.

Mary is a sacrificial lamb. Her husband wants a divorce, even though she is pregnant with their child and is a loving and devoted wife to him. He is completely willing to sacrifice (metaphorically "slaughter") this blameless woman to satisfy his own needs. He selfishly expects her to identify with and support his desires even as he is casting her off cruelly.

Additionally, Mary, the symbolic lamb, literally slaughters her husband to save herself and her unborn child from social disgrace. She is meant to take the metaphoric fall for her husband, but instead, she turns the tables and forces him to take the literal fall for her. It is completely out of character for a lamb to fight back, but this is what Mary does.

Adding even more to the layers of meaning, a literal lamb slaughters Mr. Maloney, for Mary whacks him over the head with a frozen leg of lamb.

What is the symbolism and point of view in "Lamb to the Slaughter"?

The point of view in "Lamb to the Slaughter" is third person; although, the third person perspective is not the common omniscient point of view.  We know that the story is in third person, because of the use of pronouns like "he" and "she."  If the story were written in first person, the reader would be reading "I" and "me."  The point of view is third person limited.  It is limited to Mary Maloney.  The reader knows what is going on inside of her head, but not what is going on inside of anybody else's head.  

As for symbolism, the best choice for a symbol from the story is the symbol of the lamb.  Dahl plays with this symbol quite a bit.  From the initial title, a reader could assume that a lamb is going to be killed.  Or at the very least, somebody with lamb-like characteristics will be killed.  Lambs tend to be gentle, docile, weak, and most importantly, followers.  This is how Mary is first portrayed.  When the reader meets her, it is clear that she lives for her husband, not herself.  She does not exude confidence, leadership, or strength.  Of course that all changes when she does grab hold of an actual leg of lamb.  Then the symbolic title becomes quite literal.  Mary uses a lamb to physically kill (slaughter) her husband.  

"Lamb to the Slaughter" is written in 3rd person limited point of view.  We can see this because the narrator comments on Mary's thoughts and feelings, but cannot comment on any other characters.  This differs from 1st person because 1st person uses "I" and "me".  2nd person would be written as if you, the reader, were experiencing everything.  (You walk down a hall way and turn to find a dragon!)  This also differs from 3rd person omniscient because 3rd person omniscient can comment on the thoughts and feelings of every character in the story.

As far as the symbolism, you need to be more specific.  Do you mean the theme?

The point of view is strictly that of Mary Maloney. Here is a typical example.

For her, this was always a wonderful time of day. She knew he didn't want to speak much until the first drink was finished, and she was satisfied to sit quietly, enjoying his company after the long hours alone in the house. She loved the warmth that came out of him when they were alone together. She loved the shape of his mouth, and she especially liked the way he didn't complain about being tired.

The narrator tells what Mary thinks, feels, and does. When Patrick is described, it is through Mary's point of view (POV). For example:

When he came back, she noticed that the new drink was a very strong one. She watched him as he began to drink.

The reader is not permitted to enter into Patrick's mind but can only guess what he is thinking and feeling from the way he acts, as observed by his doting wife. We know that Patrick has something important and painful on his mind because Mary sees he has made a very strong highball.

There is an excellent anthology of short stories arranged by points of view as classified by the editors, James Moffett and Kenneth R. McElheny. The full title of the book is Points of View: An Anthology of Short Stories (Rev. Ed. August 1995). "Lamb to the Slaughter" is not included in this anthology, but the editors would place it in the category they call ANONYMOUS NARRATION--SINGLE CHARACTER POINT OF VIEW. This is a very common story-telling technique. The story is told in the third person, e.g., "She watched him as he began to drink." The way Roald Dahl handles point of view in this story shows he is an accomplished fiction writer. 

Point of view is very important in story-telling because it is the chief way in which the author gets the reader emotionally involved with one of the characters. In "Lamb to the Slaughter" we sympathize and identify with Mary Maloney, even though she commits a murder, because we are held in her point of view from beginning to end. There is no one else with whom to identify without switching points of view, which can risk losing reader involvement. The other important way in which the author usually gets the reader to identify with one character is by giving that character a problem that must be solved. Mary's problem is that she has killed her husband and has to establish an alibi and dispose of the murder weapon. 

When the investigating police officers are devouring the thoroughly cooked and delicious murder weapon, they converse among themselves; but the author makes it clear that their dialogue is all being heard by Mary and that the reader is still in her point of view. Here is part of the dialogue and the very last line of the story which shows that Mary is listening to the whole conversation:

"Personally, I think the weapon is somewhere near the house."

"It's probably right under our noses. What do you think, Jack?"

And in the other room, Mary Maloney began to laugh.

From what point of view is "Lamb to the Slaughter" told, and why is this significant?

"Lamb to the Slaughter" is told from the point of view of Mary Maloney. The story starts off when she is all alone, so we have to be in her point of view at the start. Her husband's arrival, his mood, his behavior are all told through Mary's point of view. In fact, the story is largely based on her over-attentiveness, her close observation of her husband, her concern about his health, his state of mind, his appetite, his job, his drinking, and everything else about him. Patrick can't stand all this attention, all this scrutiny, all this mothering. This is what has made him decide that he wants a divorce. This in turn leads to Mary clobbering him over the head with a frozen leg of lamb.

It is important that the story is told from Mary's point of view because this enables the reader to understand why she acts as she does. Being in her point of view forces the reader to identify with her, in spite of the fact that she has committed a murder. We understand her fit of rage as a reaction to her extreme devotion to her husband and his cold rejection of her when she is six months pregnant. We understand that she doesn't want to be caught and punished. We understand her thought processes as she goes about concocting an alibi and getting rid of the evidence. We are, in fact, accessories after the fact.

The other characters are only minor ones except Patrick, who is not even a very important character himself. To narrate part of the story from the point of view of one of the policemen would disrupt the narrative flow. It is always disruptive when a writer switches from one point of view to another. To switch from Mary's to Patrick's point of view would not only disrupt the reader's identification and involvement, but it would probably generate some sympathy for Patrick which would detract from the reader's sympathy with Mary. And the author wants the reader to sympathize with, and to identify with, Mary from beginning to end. An example of how Roald Dahl avoids going into Patrick's point of view is the way he has Patrick tell Mary all his feelings about their marriage and his decision to get a divorce.

"This is going to be a big shock to you, I'm afraid," he said. "But I've thought about it a good deal and I've decided that the only thing to do is to tell you immediately." And he told her. It didn't take long, four or five minutes at most, and she sat still through it all, watching him with puzzled horror.

We don't hear a word of Patrick's case. We can only imagine what he is telling her from her reaction, i.e., from her point of view. 

...and she sat still through it all, watching him with puzzled horror.

Once Patrick is dead there is no feasible point of view other than Mary's. She has a dark secret. We alone know she is guilty and want to see her get away with her crime. The story proper really begins here. It is about how a woman commits a perfect crime by killing her husband with a frozen leg of lamb and then getting the investigators to eat the lamb after she cooks it. We have to know what she is feeling, thinking, and planning. And we have to believe in the dramatic change of character that took place in this passive, humble little housewife.

In "Lamb to the Slaughter," why is the lamb a symbol of revenge?

In the story, the lamb begins as a symbol of plenty and shared domesticity. It is a frozen leg of lamb from the couple's freezer which Mary will prepare for their dinner together. After Patrick drops the bombshell about wanting a divorce, it becomes a symbol of their discord, her distress, and ultimately of her revenge: she uses the heavy frozen lamb as the murder weapon.

In another sense, the lamb stands for the husband. Patrick is the victim, so he is figuratively a slaughtered lamb. And literally, a real lamb has been slaughtered at some previous time so it could become their meal. This lamb is also a "sacrificial lamb," giving its life to protect her as all evidence of a murder weapon has been consumed by the police.

How does the point of view change in "Lamb to the Slaughter"?

Over the course of Roald Dahl's "Lamb to the Slaughter," the point of view is always third person limited. We as readers are told about events from Mary's point of reference for the entirety of the story. She is spoken about in third person, but we learn about her emotions as though she is the one telling us how she feels.

As the story progresses, though, Mary's point of view does change. Initially, she is in disbelief over Patrick's announcement, but after killing him behaves very calmly as she goes about deciding her next steps. She wisely decides to go to the store and talk to the grocer about her plans for making Patrick dinner that night, which will give her an alibi for why she could not have killed her husband.

Upon returning home, though, Mary suddenly behaves as though she really is discovering Patrick is dead for the first time. She becomes very upset and cries. This is likely because Mary is just now fully realizing that she killed her husband. In that way, it could be argued that Mary's own perspective changes throughout the story.

How does the lamb's symbolism develop the theme of devotion's violence in "Lamb to the Slaughter"?

In “Lamb to the Slaughter,” the complex symbolism of the lamb emphasizes the story’s theme of the violence of devotion. Mary is a traditional, adoring wife who caters to her husband’s comfort. For example, she painstakingly prepares a welcome for his return home from work each day:

The room was warm and clean, the curtains drawn, the two table lamps alight—hers and the one by the empty chair opposite. On the sideboard behind her, two tall glasses, soda water, whiskey. Fresh ice cubes in the Thermos bucket.

After he walks in, she takes his coat, fixes him a drink, and sits attentively, waiting to address his needs. When she notices him finishing his first drink, she jumps up to pour him a second one and fetch his slippers. Observing that he looks tired, she offers to cook dinner at home instead of enjoying their weekly night out at a restaurant.

The lamb symbolizes Mary because she is pure and gentle. Like a lamb, she is faithful and helplessly ignorant of her husband's infidelity and her future as castoff wife and single mother. Completely devoted to her husband, she is shocked when he admits to an affair. In fact, Mary becomes a sacrificial lamb, a metaphor for an innocent person or animal sacrificed for someone else; in this case, she pays or atones for her husband’s sin of adultery. He cavalierly expects her to disappear without protest and to shoulder responsibility of their unborn baby alone. He tells her,

And I know it’s kind of a bad time to be telling you, but there simply wasn’t any other way. Of course I’ll give you money and see you’re looked after. But there needn’t really be any fuss. I hope not anyway. It wouldn’t be very good for my job.

The idiom “lamb to slaughter” describes a party who unknowingly enters danger or walks into trap. Interestingly, Mary’s husband becomes a lamb to slaughter, albeit a twisted lamb. Although not innocent like a lamb, he is ignorant of impending danger, which he unwittingly brought upon himself.

Ironically, a frozen lamb leg is the weapon Mary uses to kill her husband. She

simply walked up behind him and without any pause she swung the big frozen leg of lamb high in the air and brought it down as hard as she could on the back of his head.

Mary strikes him out of shock and rage equivalent to and caused by the depth of her devotion. His death by bludgeoning results from his callous dismissal of her devotion. Interestingly, the brutality of his murder contrasts the icy calmness of Mary moving forward.

The violence of the crash, the noise, the small table overturning, helped bring her out of her shock. She came out slowly, feeling cold and surprised, and she stood for a while blinking at the body, still holding the ridiculous piece of meat tight with both hands.

All right, she told herself. So I’ve killed him.

Her violent act transforms her from a meek wife into a clear-minded, strategic, and self-preserving woman. Mary is no longer a lamb, and the frozen lamb leg saves her from becoming a lamb to slaughter. Her husband’s infidelity and desertion are no longer threats. She is freed from her oppressive marriage into the role of a sympathetic widow. And the lamb leg is the actual tool for committing a literal slaughter of the lamb to which she devoted herself—her unfaithful and unsuspecting husband.