Sahih Bukhari Volume 6, Book 61, Hadith Number 582.

Narrated By Abdullah : That he heard a man reciting a Quranic Verse which he had heard the Prophet reciting in a different way. So he took that man to the Prophet (and told him the story). The Prophet said, “Both of you are reciting in a correct way, so carry on reciting.” The Prophet further added, “The nations which were before you were destroyed (by Allah) because they differed.”