Ibn `Umar (may Allah be pleased with him) narrated that the Messenger of Allah (peace 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." (1)
The meaning of the Hadith:
The Messenger of Allah likened the study and recitation of the Qur'an with a tied camel which is feared to run away. So, as long as a person studies and memorizes the Qur'an, it will be memorized exactly as a tied camel as long as it is tied, it will be under control. The Prophet (peace be upon him) gave example with camels because they are the more distasteful domestic animals, and trying to catch them if they run away is difficult. (3)
Lessons gained from the Hadith:
1- How fast the Qur'an is forgotten, so a person who memorizes it or memorizes parts of it should study it and keep memorizing it by revision so as not to forget it.
2- High goals are not achieved but through fatigue and hardship, and of these high goals is the memorization of the Qur'an, which is one of the great favors that is not memorized well but through frequent memorization and revision.
(1) Sahih Al Bukhari No. (4643) and Sahih Muslim No. (1313).
(2) See: Fathul-Bary of Ibn Hajar 9/ 79.
(3) Fathul-Bary, commentary on Sahih Al Bukhari of Ibn Hajar Al `Asqalany, 9/79.