The 'Abd is never afflicted with punishment more severe than hardness of the heart and being away from Allaah Subhanahu wa ta'aala. An-Naar (Hellfire) was created to melt the hard hearts. The more distant of hearts are the hard ones. When the heart hardens the eye becomes dry. The hardness of the heart stems from exaggeration in four things: eating, sleeping, talking, and socializing. As when the body becomes sick, eating and drinking cannot cure it; if the heart becomes sick with desires, preaching cannot help it.
Whoever seeks to purify his heart let him favour Allaah over his desires. The hearts are the vessels of Allaah Subhanahu wa ta'aala on His earth. The most beloved to Him are those that are most soft, most strong and most pure.
They occupy their hearts with ad-Dunyaa (the world). If they occupied them with Allaah and al-Aakhirah their hearts would wonder in the meanings of His words and His clear signs. Then their hearts would return to them with marvelous wisdoms an astonishing benefits.
Taken from AL-HIJRA Magazine vol. 3, issue 6
On the Hardness of the Heart