In Stave 5 of A Christmas Carol, Scrooge wakes up disoriented.  He does not know what day it is, and he is relieved that his possessions are still there.  It means the events of his dream did not take place.

Redemption

Scrooge asks the Ghost of Christmas Yet to Come why he would show him these visions if he was beyond all hope.  He realizes that he should, and can, and will, change.

“I will live in the Past, the Present, and the Future!” Scrooge repeated, as he scrambled out of bed. “The Spirits of all Three shall strive within me.” (Stave 5, p. 52)

Scrooge praises Marley and Christmas.  He is relieved that he is alive, and he has a chance to be redeemed.  His visions of the three ghosts have had a huge impact on him.  He has seen the error of his ways.  He is ready to be a better man.

Resurrection

Scrooge wakes up on Christmas day and is reborn.  When he comments that he knows nothing about the day, and wonders if the days have passed, it is as if he was just born.

I don't know anything. I’m quite a baby. Never mind. I don't care. I’d rather be a baby. Hallo!  Whoop! Hallo here!” (Stave 5, p. 52)

This comment is significant, because Scrooge compares himself to a baby and says he’d rather be one.  He is ready to start over, and begin his life anew.

Guilt

Once he re-orients himself, it is no coincidence that the first thing Scrooge does is buy the Cratchits a turkey.  He feels terrible about how little he knew about Cratchit’s family, and how little he has helped them.  When Cratchit comes in the next day, he playfully pretends to be angry at him for being late—and then gives him a raise.  Scrooge wants Cratchit to understand that he is a different person.

I’ll raise your salary, and endeavour to assist your struggling family, and we will discuss your affairs this very afternoon, over a Christmas bowl of smoking bishop, Bob! (Stave 5, p. 56)

He apologizes to Cratchit, and his visions of the man—and the toast—tell him that Cratchit does care about him, and will probably be receptive.  By bringing up the smoking bishop, he implies that they will be friends now.

Family

One of the reasons Scrooge was so grumpy and lonely was that he pushed people away from him.  It is no coincidence that the he becomes a better man by creating his own family out of the Cratchits and Fred.

He did it all, and infinitely more; and to Tiny Tim, who did NOT die, he was a second father. He became as good a friend, as good a master, and as good a man, as the good old city knew… (Stave 5, p. 56)

By becoming a part of Fred and the Cratchits’ lives, Scrooge not only redeems himself, but he also lives on.  One of the most important lessons Scrooge learned was the importance of family.

See here for text:  http://www.enotes.com/christmas-carol-text

What themes are linked to the ghost of Christmas past in A Christmas Carol?

In stave 2, "The First of Three Spirits," of Charles Dickens's A Christmas Carol: A Ghost Story of Christmas, the Ghost of Christmas Past suddenly reveals itself to Ebenezer Scrooge, and it appears to Scrooge to be "unearthly," otherworldly being:

It was a strange figure—like a child: yet not so like a child as like an old man, viewed through some supernatural medium, which gave him the appearance of having receded from the view, and being diminished to a child’s proportions.

Scrooge's past has also receded from view, seen from Scrooge's present perspective as an old man looking back to his childhood. The Ghost appears indistinct and contradictory at times because Scrooge's memory is likewise faded:

It held a branch of fresh green holly in its hand; and, in singular contradiction of that wintry emblem, had its dress trimmed with summer flowers.

The spring flowers trimming the Ghost's dress represent the springtime of Scrooge's life. Springtime is long past, however, both in terms of the actual time of the year, this being December, and more symbolically in terms of the part of Scrooge's life that no longer exists:

But the strangest thing about it was, that from the crown of its head there sprung a bright clear jet of light, by which all this was visible; and which was doubtless the occasion of its using, in its duller moments, a great extinguisher for a cap, which it now held under its arm.

A little later in the stave, when Scrooge and the Ghost are walking along the road to the town where Scrooge grew up, the Ghost tells Scrooge that the events he witnesses and the people he sees "are but shadows of the things that have been.”

Without light there can be no shadows. The Ghost's light illuminates Scrooge's life, allowing him to see into the long-forgotten shadows of his past. It allows Scrooge to see the effect of the choices he made, particularly when he decided to abandon Belle, the woman to whom he was betrothed, in order to devote his life to the pursuit of wealth.

The Ghost's light also illuminates a path for Scrooge out of his past. It allows him to recognize the consequences of the choices he made early in life and to move beyond those choices and beyond the limitations of his past.

At the end of the Ghost's visit with Scrooge, the Ghost's light seems to grow even brighter, and Scrooge tries to extinguish the light with the Ghost's cap:

The Spirit dropped beneath it, so that the extinguisher covered its whole form; but though Scrooge pressed it down with all his force, he could not hide the light: which streamed from under it, in an unbroken flood upon the ground.

Symbolically, the Ghost's light illuminates the way for Scrooge's to find his way to a release and redemption from his past.