The Prophet (pbuh) said:
“Undoubtedly, the heart gets rusted like metal gets rusted when water goes over it. The People asked, “How can they [hearts] be cleaned.” The Prophet (Pbuh)replied, “To remember death in abundance and to recite the Holy Quran.” (Mishkat)

In another hadith the Prophet (pbuh) said:
“That chest which does not have any Quran in it is like an abandoned house. (Tirmizi)