While answering this question, let us immediately state that those who boast about the sins they committed and do not regret them are out of our scope. Our main subject is those who fall into such sins even though they believe and regret them.
The Mu’tazilite sect and some of the Kharijites outside the Ahl as-Sunnah say that “those who commit major sins will become infidels or remain in the middle between faith and disbelief” and they try to explain this as follows:
“The faith of a believer who commits one of the major sins is lost. Because it is not possible for someone who believes in God Almighty and approves of hell to commit a major sin. “If a person who protects himself illegally out of fear of being imprisoned in this world commits major sins without thinking about the eternal torment of hell and the wrath of God Almighty, it certainly indicates his lack of faith.”
This judgment, which seems correct at first glance, is the product of a faulty thought that does not know the nature of man. Bediüzzaman Said Nursi gives the answer to this question in his work titled Lem’alar as follows:
“… If the feeling prevails in a person, he will not listen to the reasoning of the mind. He is dominated by desires and delusions, and prefers a minimal and insignificant pleasure to a great reward in the future. And he is more afraid of a small present trouble than of a great torment in the future (a postponed torment that will come later) . Because imagination, enthusiasm and feeling do not see the future. Maybe they deny it. Even if the soul helps, the heart and mind, which are the locus of faith, remain silent and are defeated.”
“In this case; Committing great sins does not come from unbelief, but perhaps from the defeat of the mind and heart due to the overpowering of feelings, desires and delusions.”
Yes, as Bediuzzaman Said Nursi stated, there is a characteristic in man’s nature that he sees the incomprehensible pleasures of heaven as far beyond, and therefore puts them in the background and inclines towards the pleasures of sin that are right at hand. This is the secret of why a man, who went to the nearest restaurant because he was very hungry, started gnawing the dry bread he had at hand and filled half of his stomach with it, because the two-portion kebab he ordered would be 10-15 minutes late.
Again, as Bediüzzaman said, a person is more afraid of a slap he is about to receive than the solitary confinement he will be in after a month. In other words, according to this feeling, the torment of hell is very far away for him and God is already forgiving.
With these considerations, a person – despite being a believer – tends to commit sins and may fall into them with the support of his soul. Yes, committing major sins does not come from unbelief. However, if those sins are not destroyed immediately through repentance, they can lead people to disbelief. Let’s listen to Bediüzzaman again on this subject:
“Sin penetrates the heart and turns it black and hard until it brings out the light of faith . In every sin, there is a path to blasphemy (denial of Allah) . If that sin is not destroyed quickly by asking for forgiveness, it bites the heart not as a wolf but as a small spiritual snake…” (see Flashes, Second Flash)