Imam sheds the light on the topic in his famus book of "the combat with the self" as following:
If any worldly affair is a cause for man’s attention to be directed toward the world and to neglect God, the Exalted, it raises dark veils. All of the corporeal worlds are dark veils. If the world is a means of directing attention to the Truth and for arriving at the abode of the Hereafter, which is the “abode of honor,” then the dark veils are transformed into veils of light.
“Being perfectly cut off from all else” means tearing and pushing aside all the dark and light veils, until one is able to enter the divine guest house which is the “source of greatness.” Hence, in this intimate devotion (munajat) there is a request to God, the Exalted, for vision and brightness of the heart so one may tear the veils of light and reach the source of greatness: “Until the vision of the heart tears through the veils of light, so that there is union with the source of greatness.”
However, one who has not yet torn the veils of darkness, one who directs all of his attention to the natural world and, God forbid, becomes deviated from Allah, and one who is basically unaware of the world beyond and the spiritual worlds, and has retrogressed to a state of nature, who has never decided to refine himself, to set into motion his spiritual powers, to push aside the curtains of darkness which are a cloud over his heart, Imam further explained.
He is lodged in ‘the deepest of the depths’ [of hell] which is the ultimate veil.
“Then we render him the lowest of the low” (Q 95:5),
While the God of the worlds has created man in the most lofty state and station.
“Indeed we have created man in the best of molds” (Q 95:4).
If one follows the desires of the self and from the day he becomes acquainted with himself pays no attention to anything other than the dark wilderness and never thinks that it is possible that aside from this polluted dark world that there exists another place and station, then he will have sunk into the veil of darkness and have become an instance of,
“But he clung to the earth and followed his low desire” (Q 7:176).
With such a heart polluted by sin that he has been covered by the curtain of darkness, and with such a gloomy spirit that due to the effect numerous sins he has become far from God, the Exalted, that worship of desire and seeking after the world have blinded the intellect and eyes of truth, then he cannot be released from the veils of darkness, let alone to tear the veils of light and detach himself from all but Allah.
The strongest sort of belief he might have would be not to deny the position of the saints [awliya] of God, and not to consider as myths the worlds of the barzakh, the sirat, the resurrection, the accounting, the book, heaven, and hell. Due to the effects of sins and the attachment of the heart to this world, one comes to gradually deny these truths, to deny the positions of the saints [awliya] of God, positions which are mentioned in not more than a few lines of prayers and intimate devotions.
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