Sahih Bukhari
Sahih Bukhari Volume 006, Book 061, Hadith Number 549.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 61. Virtues of The Qur'an
Narrated By Ibn Umar : Allah's Apostle said, "The example of the person who knows the Qur'an by heart is like the owner of tied camels. If he keeps them tied, he will control them, but if he releases them, they will run away."