Prophets invite people to the inherent

 goodness and cleanliness. In order to fulfill this duty, Allah (swt) has given the prophets some knowledge in special ways. This knowledge constitutes the divine books. In order to be a believer, it is necessary to believe that Allah (swt) has revealed books for people through prophets. This faith includes believing both in the books revealed to the prophets before the Prophet Muhammad (saw) and the Qur'an that revealed to Him. (Baqarah, 2/4; 285) In general, it is necessary to believe in all the divine books, as well as in the books mentioned in the Qur'an one by one. Because all the divine books revealed for the same purpose. The messages they give are essentially the same. For this reason, those that come after are in the nature of confirming the previous ones. But believing in the books before the Qur'an means believing in their pristine purity, that is, believing in them as the way they revealed by Allah.