Narrated Ibn Az-Zubair:
I said to `Uthman, "This Verse which is in Surat-al-Baqara: "Those of you who die and leave widows behind...without turning them out." has been abrogated by another Verse. Why then do you write it (in the Qur'an)?" `Uthman said. "Leave it (where it is), O the son of my brother, for I will not shift anything of it (i.e. the Qur'an) from its original position."
USC-MSA web (English) reference: Vol. 6, Book 60, Hadith 60
Arabic reference: Book 65, Hadith 4536