Personification is the description of an inanimate object as if it were human, and it can be seen at a number of different points throughout the novel. One good example, however, comes just after Bill Sikes has murdered Nancy, and is used to describe the sun as it rises the next day:
The sun--the bright sun, that brings back not light alone, but new life, and hope, and freshness to man--burst upon the crowded city in clear and radiant glory. Through costly-coloured glass and paper-mended window, through cathedral dome and rotten crevice, it shed its equal ray. It lighted up the room where the murdered woman lay.
Note how the sun is described as "bursting" upon London as it spreads its bright rays everywhere. In a sense, this personification describes the sun as if it were a person "bursting" into a room, so sudden is its arrival and the way that it brings joy and light to everything and shines its rays upon all objects, even those such as the body of Nancy. This example of personficiation is actually important because it also captures an important use of imagery throughout the novel, which is the way that light and dark imagery is used to capture the goodness of certain characters such as Oliver and the way that this goodness is threatened by other characters such as Fagin and Sikes.