It was narrated that Abu Hurairah said:
"The Messenger of Allah said: 'Learn the Qur'an, recite it and go to bed, for the likeness of the Qur'an and the one who learns it and acts upon it is that of a sack filled with musk, which spreads its fragrance everywhere. And the likeness of one who learns it then goes to bed with it in his heart is that of a sack that is tied up from which no fragrance comes out.'"
English reference: Vol. 1, Book 1, Hadith 217
Arabic reference: Book 1, Hadith 222