Virtues of the Qur'an -7
narrated ibn umar (radi-allahu 'anhu):
allah's apostle (sallallahu 'alaihi wa sallam) 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."
bukhari vol. 6 : no. 549