When the people asked the Prophet about the cure and the method to clean the qalb, he said, “Frequent remembrance of death and recitation of the Quran.”[Bayhaqi]
The Prophet (peace be upon him) has said that hearts get rusted in the same way that iron rusts when it is wet. He further stated that when man sins, a dark spot appears on the qalb. And when he does not repent or relent and continues to sin, another dark spot covers the qalb until finally the entire qalb is rusted and turns black. When the people asked the Prophet about the cure and the method to clean the qalb, he said, “Frequent remembrance of death and recitation of the Quran.”.[Bayhaqi]
Accordingly, one must often remember death and the eventual meeting with Allah on the Day of Judgment; and a person must regularly recite the Quran. It is these things which cure a defective qalb, remove its rust, and cleanse its blackness. That is when it starts to glow. The nur (light) of iman (faith) is reborn within it and the whole life is rejuvenated. When the link between the qalb and Allah is established and the qalb starts to resonate with the remembrance of Allah, then the qalb will be set on the right path.
(Compiled From: “A Righteous Heart: The Axis of One’s Deeds” – Khurram Murad)