"Our scholars and pious predecessors have noted that every disobedience of Allāh ta'ālā carries within itself the taint of kufr (disbelief) to some degree. This is why one who is constantly involved in sins is considered to be endangering his imān.

A flagrant sinner will be disinclined to repent, and may eventually land himself in destruction by beginning to question faith, and eventually denounce faith in Allāh ta'ālā altogether (may Allāh ta'ālā protect us)."