Ibn al-Mubarak said:

‘How many people carry the Qur’an in the hearts but the Qur’an curses them from inside their hearts! If the bearer of Qur’an disobeys his Lord, the Qur’an calls him from inside his chest saying, ‘By Allah, you have not carried me (i.e. memorised me) for this! Will you not be shy from your Lord?’