Which particular words are you refering to? I wonder if your question relates to the following lines of this chapter, which is of course a key moment in this brilliant novel, as Rochester finally proposes to Jane and she accepts him:
Again and again, he said, "Are you happy, Jane?" And again and again I answered, "Yes."
This of course, as we understand having read the rest of the book, is important because Rochester is trying to justify what he is doing, which is committing bigamy as he takes a second wife. He is trying to reassure himself that his actions are not only selfish and for his own happiness, but that they are giving happiness to Jane as well as himself. This strategy therefore is something that should make the astute reader sit up and take notice. Why is it that he is so desperate to assure himself that Jane is happy, and why does he feel the need to make "atonement" for this act which Rochester refers to as being against the judgement of the world. The repetition therefore is used to foreshadow the events that befall their relationship later on in the novel.