These Divine Specialists have described that the heart of an infidel is a reversed or over-turned heart which does not contain any goodness in it. Such heart' is deviated from its primordial nature; does not look towards the Upper-Heavens and keeps itself amused and preoccupied into worldly affairs, therefore, it does not witness the existence of God-Almighty and I. Eternal-World. It lacks the proper imagination for goodness and righteous deeds, because, the righteous deeds reach the perfection stage and Gods-Nearness only in cases when they are performed with the intention of attaining His pleasure. But since an infidel has reversed his heart, he does not see God-Almighty any more, and therefore, does not have any other aim except this world in all his affairs.
Such an heart in his primordial nature was blessed with esoteric eyes which now have been blinded because, he cannot witness the most explicit shinning realities i.e. the Creator of the Universe. He is blind and will be raised as blind in the Next World too. In this world he is attached to worldly affairs, and will be raised in the Next World possessed with the same attachment, but since the Eternal-World lacks these worldly amusements, he will burn with the fire of separation. In such heart the light of faith has been extinguished and therefore, it is totally filled with absolute darkness.
5.2.2. The Heart of a Believer
Just opposite to the heart of an unbeliever is the heart of a perfect righteous believers; whose doors are open towards the Upper-Heaven and Unseen-World; is illuminated with the light of faith which will never be turned off; and through its two esoteric eyes witnesses the mysteries of the Hidden-World. Such a heart continuously strives for achieving absolute t perfection, beauty and salvation and seeks God's Pleasure and Blessing. Since he wants God-Almighty therefore, continuously strives to move in His Direction by means of good moral conduct and righteous deeds. Such heart is wider than the Celestial Sky and Divine Thrown, beautiful than the Paradise, is the Divine Treasure and center of manifestation of Heavenly Light; his earth is enlightenment, his sky is faith; his sun is enthusiasm for God's countenance; his moon is God's love; where the wisdom rules and absorbs the rain of Divine Blessings for producing the fruits of worship and obedience; is filled with absolute light, joy, cheerfulness, purity, and will be raised in the next world in the similar state.
5.2.3. The Heart of a Believer- Occasionally Contaminated
The heart of a believer which occasionally gets contaminated with sin is not dark and confined rather is illuminated with the light of faith and remained open for receiving guidance and Divine Blessings. But as a result of sinning it has developed a black spot and Satan has succeeded to make an entry into it. Although, the esoteric eyes are not quite yet blinded but because of sinning have caught a disease which might render them blind. Both angels as well as Satan have access within such heart. The angels enter through the doors of faith and invite him towards goodness while the Satan influences through the black spot inviting him towards evil.
In such a heart both Satan and angel are engaged in a continuous confrontation. Angle wants to take over the control of entire heart forcing Satan out through good deeds on the other side Satan through seduction and sins makes the darker heart further darkest and strives to take over the control of entire heart by forcing out the angel and permanently closing the gateway of belief forever. These two are permanently engaged in a continuous war until one of them become victorious over his opponent, and what is the magnitude of victory achieved. The esoteric life and eternal destination of human being depends upon this struggle. It is here that the struggle with the self becomes of crucial importance, which will be discussed later on in the book.
5.3. Hard-heartedness
In his initial primordial nature the heart is bestowed upon with special virtues such as purity, enlightenment, kindness, and blessing. He is sensitive towards other people's difficulties and feels un-comfortable while seeing others in pain even animals. He desires that others should live a pleasant and comfortable life and takes pleasure in doing favors towards them. In accordance with his pure nature is inclined and pays attention towards God-Almighty; takes pleasure in performing worship, prayer, supplication, and other righteous deeds, while immediately feels ashamed and offer repentance if commits sins.
In case the heart accepted invitation of his pure primordial nature and acted accordingly, he becomes purest, kindest, sincerest, and enlightened, because of the effects of worship and prayers his enthusiasm and love for these things increases day by day. But if he neglects and acts against his inner natural feelings and sentiments, they gradually get subdued and eventually become completely silenced and eventually annihilated.
If after seeing the horrible tragic scenes involving others does not show any reaction, gradually becomes used to such things to the extent that further repetition of such encounters will produce least reaction. Also, it is possible that one may reach to a point where seeing the poverty, hunger, and wretchedness involving others not only produce any disturbance with in his conscience on the contrary while seeing the painful scenes of imprisonment, torture, and murders feels happy and pleased. [1]
If someone commits a sin for the first time, he feels guilty and ashamed about it, but having committed a sin for the first time, to repeat it for the second and third time relatively becomes easier for him, and in case of his persistence in sinning reaches to a point, where not only he does not feel any sense of guilt and shame, on the contrary considers himself victorious and feels happy.
The heart of such persons has become dark and reversed and in the words of the Holy Quran and narrations has acquired hard-heartedness. Satan has occupied these hearts forcing the God's Angels out, and the doors of salvation have been closed permanently leaving no hope for repentance and return towards God-Almighty.
The God-Almighty said in the Holy Quran:
"If only, when our disaster came on them, they had been humble! But their hearts were hardened and the devil made all that they used to do seem fair unto them!" -the Holy Quran (6:43)
And said:
"Then woe unto those whose hearts are hardened against remembrance of God. Such are in plain error.” -the Holy Quran (39:22)
Imam aI-Baqir (A) said:
"There is a white spot inside the heart of each believer. Once he commits a sin or repeats it, a black spot appears inside the heart. In case of persistence of sins, the black spot, increases, gradually in size filling the entire heart with blackness. When this happens the owner of such heart never returns towards goodness, and this, is what God meant in the verse:
"Nay, but that which they have earned is rust upon their hearts." -Bihar al-Anwar, vol. 73, p-361.
The Commander of the Faithful Imam' Ali (A) said:
"The tears of eye never get dried but for the sake of hardheartedness,. the heart never acquires hard-heartedness but for the sake of excess of sins." -Bihar al-Anwar, vol. 73, p-354.
The Holy Prophet (S) said:
"The following four things are the indicators of human cruelty:
1) Dryness of eyes (ii) Hard-heartedness (iii) Excessive greed for earning a living (iv) And persistence of sins. -Bihar al-Anwar, vol. 73, p-349.
It was because of this reason that the Infallible Imams (A) of prophet's progeny in their supplications took shelter in God-Almighty against hard-heartedness.
Imam al-Sajjad (A) said:
"Oh God! I do complain to you against hard-heartedness –the heart which by means of whims and passions is in the state of continuous revolution and has become contaminated. And I do complain to you against the dryness of eye which does not cry and is not afraid of you, and instead takes pleasure in looking towards whatever makes it pleased."
--Bihar al-Anwar, vol. 94, p-143.
Therefore, a human being who desires his own prosperity and soundness of heart must prevent himself from committing any sin however small it might seems; should gradually motivate his self for performing righteous deeds namely: worship, prayer, communications with God, sincerity, kindness and help towards others, defense of oppressed and deprived, benevolence, and cooperation for achieving social welfare and social justice, so that it performs them as a matter of habit. His inner purity and illumination continues striving for perfection and purification fill his heart becomes a special center of God's favorite angels.
source : http://www.islamicecenter.com/e-library/logic_islamic_rules/logic_islamic_rules_makarem_subhani_03.html