﴿ إِنَّ ٱلَّذِينَ كَفَرُوا۟ بَعْدَ إِيمَٰنِهِمْ ثُمَّ ٱزْدَادُوا۟ كُفْرًۭا لَّن تُقْبَلَ تَوْبَتُهُمْ وَأُو۟لَٰٓئِكَ هُمُ ٱلضَّآلُّونَ ﴾

“Verily, as for those who are bent on denying the truth after having attained to faith, and then grow [ever more stubborn] in their refusal to acknowledge the truth, their repentance [of other sins] shall not be accepted: for it is they who have truly gone astray.”

Not acknowledging any truth external to their community appears to be a bid to save their faith. But in actuality it destroys their faith. God’s true believer lives on God’s continuous inspiration, so that one who confines himself to self-worship and community-worship will be blocking all paths to God’s blessing entering into him. After being deprived of God’s inspiration, what will there be left with which to nurture his faith?