We Believe Allah sent down books to his Messengers and prophets to aid them in conveying his commands:
"Indeed, We have sent Our Messengers with clear proofs and revealing with them the Book and the Balance (justice) that mankind may stand forth in justice." 
"Mankind were one community and Allaah sent Prophets with glad tidings and warnings, and with them he sent the Book in truth to judge between people in matters wherein they differed."