Narrarated Abdullah (RAA): The Prophet (PBUH) said, "It is
a bad thing that some of you say, 'I have forgotten such and such
a Verse of the Qur'an', for indeed, he has been caused (by Allah)
to forget it (because of neglecting the Qur'an and not reciting
it frequently). So you must keep on reciting the Qur'an because
it escapes from the hearts of men faster than camels do (when they
are released from their tying ropes)" (Bukhari)