There is no official line, but three from the book itself gather what it asks: "am I a louse, like everyone else, or a man?", "Was it the old woman I killed? It was myself I killed, and not the old woman!" and the one that turns the page in the Epilogue, "In place of dialectics came life."
The first is Raskolnikov's to Sonia, in the confession. He explains that he needed to know "am I a louse, like everyone else, or a man?" and adds: "Will I be able to overstep or won't I!" It is the question that led him to the ax: the crime was, above all, a test of himself.
The second comes right after, and shows the punishment, because he did not kill only the old woman, he killed himself. The third is the narrator's, in the Epilogue, and closes the novel without closing the story: life arrives in the place of reasoning.
One sentence deserves caution, because read on its own it sounds like comfort: "Pain and suffering are always required of a broad conscience and a deep heart." In the text, it is Raskolnikov answering Razumikhin, at Porfiry's house, about the extraordinary men who would have the right to kill and, for that reason, should suffer. There are two readings: a lament from someone who already suffers for what he did, or an attempt to give the theory a side that redeems it.