How do we believe in heavenly books that are not in their original form, and what is the reason for the previous books not being preserved from human interference?

Belief in the divine books means a firm conviction that Allah sent down books to His prophets and messengers, and that the Holy Quran abrogated all of them. Therefore, it is not permissible to act upon any ruling from the previous books except what the Quran has affirmed, nor is it permissible to look into the books of the People of the Book. The reason these books were not preserved is that Allah Almighty did not undertake to preserve them; rather, He entrusted their preservation to humans, leading to their distortion, unlike the Quran, which Allah Himself guaranteed to preserve.