Sahih Bukhari Volume 4, Book 56, Hadith Number 682.

Narated By Ibn Mas’ud : I heard a person reciting a (Quranic) Verse in a certain way, and I had heard the Prophet reciting the same Verse in a different way. So I took him to the Prophet and informed him of that but I noticed the sign of disapproval on his face, and then he said, “Both of you are correct, so don’t differ, for the nations before you differed, so they were destroyed.”