The Qur'an recognizes all the scriptures that had been revealed before its own time. However, the Qur'an does not, in an explicit fashion, state the total number of all such revealed scriptures. There is only the mention of the names of four other scriptures in the Qur'an. These include the Taurat which was revealed to the Prophet Moosa (a), the Zaboor which was revealed to the Prophet Dawood (a) the Injeel which was revealed to the Prophet Isa (a) and the Qur'an itself which was revealed to the Prophet Muhammad (e). The Qur'an further highlights the fact that besides these four scriptures, other edicts, too, were revealed by the Lord Creator.
'Say : We believe in Allah and what is revealed to us and what was revealed to Abraham and Ishmael and Isaac and Jacob and the tribes, and what was entrusted to Moses and Jesus and the prophets from their Lord.' (3:136)
'And this is in the Books of the earliest (Revelations), The Books of Abraham and Moses.' (87:18,19)
The Qur'an attests the truth of all the previous scriptures. 'It is He Who sent down to thee (step by step), in truth, the Book, confirming what went before it; and He sent down the Torah (of Moses) and the Gospel (of Jesus).' (3:3)
It is the compulsory duty of the Muslim to believe in all the scriptures that were revealed by Allah. Indeed, the Qur'an views the disbelief in the divine nature of any of the previous scriptures as a gross perversion.
'O ye who believe! Believe in Allah and His Messenger, and the scripture which He hath sent to His Messenger and the Scripture which He sent to those before (him). Any who denieth Allah, His angels, His Books, His Messengers, and the Day of Judgment, hath gone far, far astray.' (4:136)