An example of personification is "Oliver and Nature fought out the point between them" (Ch. 1).

Personification is when you describe something inanimate or not human as if it were a person or had human-like qualities.  One of my favorite examples of personification from Oliver Twist occurs in the very beginning.

Oliver and Nature fought out the point between them. The result was, that, after a few struggles, Oliver breathed, sneezed, and proceeded to advertise to the inmates of the workhouse the fact of a new burden having been imposed upon the parish… (Ch. 1)

The personification is the first sentence.  Nature is being personified.  Basically, what it means is that Oliver lived.  The second part of the sentence means that Oliver cried, and I include it because I think it is funny and poignant too.

Poor little Oliver Twist did not begin his life very easily.  His mother had an affair and essentially only succeeded in walking herself to the parish and dying.  He was born, and barely survived.  Dickens says that it was a miracle that he did survive, because he had trouble breathing.  Ironically, no one tried to save him, so he was left to fight it out himself, and that is why he did live.

Now, if, during this brief period, Oliver had been surrounded by careful grandmothers, anxious aunts, experienced nurses, and doctors of profound wisdom, he would most inevitably and indubitably have been killed in no time. (Ch. 1)

This is where Oliver had his fight with Nature.  Nature was in some ways, his own body and his struggle for survival was with his lungs.  He won!  The point goes to Oliver.  He lived, spindly and tiny though he was.  It was an uphill battle for the poor guy from there of course, but you have to start somewhere.

Personification is used by authors, along with other figurative language, to paint a picture in the reader’s head.  In this case, it helps with the satire and adds to the humor, but it also helps to create a very clear image to build up for the reader the idea of the poor little baby struggling for life.