A summary of the concepts held by the Ahl al-Sunnah.
The hardness of the heart, its lack of tenderness, and its lack of humility.
There are several causes for the heart’s hardness and lack of tenderness.
The primary cause is a weak knowledge of Allah—Mighty and Majestic is He—and of His Most Beautiful Names.
This results in a weakened sense of reverence for Allah Almighty within the heart.
And a diminished fear of Him, Glorified be He.
Consequently, all other spiritual ailments of the heart follow.
Another cause is the heart being filled with the love of this world and its desires.
For how could a heart that is scattered across the paths and valleys of this world,
Truly contemplate, soften, or humble itself before the majesty and greatness of Allah?
When the abundance of sins and acts of disobedience is added to this love of the world,
The hardening of the heart becomes entrenched, as the Almighty said:
“Nay, but that which they have earned is rust upon their hearts.” (83:14)
Meaning, their sins have covered and veiled their hearts.
The Prophet, peace and blessings of Allah be upon him, said:
"When a believer commits a sin,
A black spot appears on his heart.
If he repents, desists, and seeks forgiveness,
His heart is polished.
But if he increases in sin, the spots increase,
Until his heart is covered by the 'ran' (rust) that Allah, Mighty and Majestic is He, mentioned in the Qur'an."
Narrated by Ahmad and al-Tirmidhi, and classified as hasan by al-Albani.
When the heart hardens and humility departs from it,
It may manifest only in the body,
A false, hollow humility that some of the salaf called,
The humility of hypocrisy.
This is when the body appears humble,
While the heart is not humble at all.
The person with a hard, petrified heart,
Is not benefited by signs or exhortations.
The words of Allah Almighty hold true for him:
“Will they then not meditate on the Qur'an, or are there locks on the hearts?” (47:24)
Nor are they turned back by calamities and trials.
Rather, he becomes one of those who turn away,
As the Almighty said:
“How many a portent is there in the heavens and the earth which they pass by with face averted!” (12:105)
And they are turning away from them.