
Hazrat Shaikh Moulana Muhammad Zakariyya (rahmatullahi ‘alaih) mentioned in Fazaa’il-e-A’maal:
Due to excessive sinning and being negligent from remembering Allah Ta‘ala and making His zikr, the hearts become rusted, just as iron rusts when it comes into contact with water. Reciting the Qur’aan Majeed and the remembrance of death cleanses and polishes the rusted hearts.
The heart is like a mirror. If the heart is dirty, then it will not reflect the ma’rifat (recognition) of Allah Ta‘ala, and the more polished and brighter the heart is, the more it will reflect the ma’rifat of Allah Ta‘ala. Therefore, to the extent a person commits sins, whether sins pertaining to lust or other evil deeds, will he lose the recognition of Allah Ta‘ala.
In order to polish the mirror of the heart, the Mashaayikh encourage their mureeds (disciples) to engage in spiritual exercises, make mujaahadah (strive to oppose the nafs in fulfilling the command of Allah Ta‘ala), to complete their ma’mulaat (daily nafl ibaadat) and daily prescribed acts of zikr.
It is mentioned in the Ahaadith that when a person commits a sin, then a black spot appears on his heart. If he makes sincere taubah, this black spot is removed. If he commits another sin, then another black spot appears. In this way, if he goes on committing sin after sin, then due to the abundance of the black spots, his heart gradually becomes completely black (as the black spots envelop his heart). Thereafter, the heart will not find the desire to do good deeds, rather the heart will be inclined towards committing sins and evil deeds – may Allah Ta‘ala save us from this!
The following verse of the Qur’aan Majeed indicates towards this:
کَلَّا بَلۡ رَانَ عَلٰی قُلُوۡبِهمۡ مَّا کَانُوۡا یَکۡسِبُوۡنَ ﴿۱۴﴾
Never (the verses of the Qur’aan Majeed are not fables, but the absolute truth)! In fact, (the reason why they do not believe is that) the rust of their sins has covered (sealed) their hearts (so no truth can penetrate it).” (Surah Mutaffifeen v. 14)
(Fazaa’il-e-A’maal [Urdu] pg. 234-235)
Ihyaaud Deen An Effort to Revive Deen in Totality