Belief in Books of ALLAH (كتب الله)
ALLAH ( الله سبحانه و تعالى ) has sent down many books with his prophets (نبي) to guide human towards Allah’s straight path and not falling in Shaytaan's (الشيطان) tricks
This is the list of books sent by ALLAH ( الله سبحانه و تعالى )
• The Tawrah (التوارة). This was given to Prophet Musa (النبي موسى).
• The Zahour (زبور). This was sent to Prophet Dawud (النبي داود).
• The Injeel (الإنجيل). This was reviled on Prophet Isa (النبي عيسى).
• The Quran (القرآن الكريم). This was revealed on the last Prophet Muhammad (محمد صلى الله عليه وسلم).
ALLAH ( الله سبحانه و تعالى ) has sent all these book so human can stay on the right path even in absence of their prophets. But with the time human has made changes in these books to what they like rather than what ALLAH ( الله سبحانه و تعالى ) told them.
The only book that is still in it's original form is The Quran. This is the last book and there is no book after Quran as their is no more prophet after Prophet Muhammad (محمد صلى الله عليه وسلم). That is why ALLAH ( الله سبحانه و تعالى ) decided to protect it by himself
Indeed, it is We who sent down the Qur'an and indeed, We will be its guardian. (Surah 15, Ayah 9)