Person Who Knows Qur'an By Heart Is Like Owner Of Tied Camels…

Narrated Ibn Umar (may ALLAH be pleased with him):

ALLAH's Apostle (peace and blessings of ALLAH be upon him) 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."

Reference:
[Sahih Bukhari (Book #61 Hadith #549)]