Reference: Fataawa Noor ‘alad-Darb – Question No.6194, Pages 18-19, Volume 12
Question: What are the causes of the hardening of the heart, and the cure for that?
Response: [From] the causes of the hardening of the heart are avoiding and distancing oneself from Allaah (‘Azza wa Jall) and the recitation of the Qur.aan; [this is in addition to] busying oneself in [the affairs of] this world, such that [the affairs of] this world become the most important of all his thoughts, and as a result he is not concerned with the affairs of his religion. [As we know] obedience to Allaah (‘Azza wa Jall) necessitates the softening of the heart, and it’s tenderness, as well as it returning back to Allaah (Tabaara-kAllaah).
And the remedy for that is to turn to Allaah [in worship], and increase in His remembrance and the recitation of the Qur.aan, as well as other acts of worship – according to [the best of] one’s ability.
We ask Allaah for ourselves and our brothers [and sisters] that he softens our hearts to His remembrance, and to prolong it upon His obedience, for indeed He is All Capable over everything.