And if he outwardly confesses the prophethood of the Prophet while inwardly harboring doctrines that are unanimously recognized as disbelief, he is a "Heretic" [al-Zindiq].'

And from Kitab al-Tajrid: 'Verily, the primordial disposition [jibillah] of the believers was never subject to discordance, and the primordial disposition of the disbelievers was never subject to harmonious alignment. Consequently, upon the occurrence of the cosmic disruption [al-ikhtilal], they broke away and were distinctly separated unto the Left, and the decree of punishment was justly actualized against them as an existential consequence, a burden, and an exemplary deterrent because of their denial of their Creator and their rejection of Him—for He is their Cause of death and their Giver of life.

Thus, the soul of the believer became inherently Luminous through their primordial affirmation, compliance, and righteous deeds; whereas the soul of the disbeliever transformed into something Demonic due to its rebellion against its Creator and its abandonment of righteous deeds.

"[187] And al-Sadiq—His glory is mighty—stated: 'Allah fashioned the believers from His own Light, and He fashioned the disbelievers from the lapse [zallah] of the believers.'