Our belief in the divinely revealed books is one of the pillars of our faith; without it a Muslim’s faith is not valid. The divinely revealed books are a manifestation of God’s care for humanity, and His Lordship over creation. Our Lord revealed books to us and commanded His Messengers to convey them, and it is Muslims’ responsibility to believe in the divinely revealed books on a whole. Muslims must believe that God revealed books to humanity that make Him known to them and teach them how to worship Him. Our Lord revealed the Quran to Muhammad, and before that He revealed other books, He hath revealed unto thee (Muhammad) the Scripture with truth, confirming that which was (revealed) before it, even as He revealed the Torah and the Gospel [3:3]. Muslims must believe in the information that the divine law has provided concerning these previous revelations.
Muslims believe that God revealed pages to Abraham and that He revealed the tablets and the Torah to Moses, Lo! This is in the former scrolls. The Books of Abraham and Moses [87:18-19]; Or hath he not had news of what is in the books of Moses. And Abraham who paid his debt [53:36-37]; Hath there not come unto them the proof of what is in the former scriptures? [20:133].
We also believe that God revealed everything to Moses in the Tablets, He said: O Moses! I have preferred thee above mankind by My messages and by My speaking (unto thee). So hold that which I have given thee, and be among the thankful. And We wrote for him, upon the tablets, the lesson to be drawn from all things and the explanation of all things, then (bade him): Hold it fast; and command thy people (saying): Take the better (course made clear) therein. I shall show thee the abode of evil-livers [7:144-145]; Again, We gave the Scripture unto Moses, complete for him who would do good, an explanation of all things, a guidance and a mercy, that they might believe in the meeting with their Lord [6:154]; We gave unto Moses the Scripture, and We appointed it a guidance for the children of Israel, saying: Choose no guardian beside Me [17:2].
We also believe that God revealed the Zabur to David, And thy Lord is Best Aware of all who are in the heavens and the earth. And we preferred some of the prophets above others, and unto David We gave the Psalms [17:55]; Lo! We inspire thee as We inspired Noah and the prophets after him, as We inspired Abraham and Ishmael and Isaac and Jacob and the tribes, and Jesus and Job and Jonah and Aaron and Solomon, and as We imparted unto David the Psalms [6:163].
And we believe that God revealed the Injil to Jesus son of Mary, And We caused Jesus, son of Mary, to follow in their footsteps, confirming that which was (revealed) before him in the Torah, and We bestowed on him the Gospel wherein is guidance and a light, confirming that which was (revealed) before it in the Torah - a guidance and an admonition unto those who ward off (evil) [5:46]; When Allah saith: O Jesus, son of Mary! Remember My favour unto thee and unto thy mother; how I strengthened thee with the holy Spirit, so that thou spakest unto mankind in the cradle as in maturity; and how I taught thee the Scripture and Wisdom and the Torah and the Gospel [5:110].
Muslims believe that God revealed pages to Abraham, the Torah to Moses, the Psalms to David, and the Bible Injil to Jesus. Muslims do not deny or affirm the names of any books revealed to the prophets without being informed about them by a legal text. Muslims do not believe that these books have been entirely preserved by God along the years or that they include a law that is to be followed by Muslims for two reasons:
The first is that God has not mentioned that He has preserved these books until now, rather He has mentioned that the Jews altered them, and these books were, before the coming of Islam were revealed to the Jews. Therefore woe be unto those who write the Scripture with their hands and then say, "This is from Allah," that they may purchase a small gain therewith. Woe unto them for that their hands have written, and woe unto them for that they earn thereby [2:79]; And because of their breaking their covenant, We have cursed them and made hard their hearts. They change words from their context and forget a part of that whereof they were admonished [5:13]; Have ye any hope that they will be true to you when a party of them used to listen to the word of Allah, then used to change it, after they had understood it, knowingly?[2:75]; Say O People of the Scripture! Ye have naught (of guidance) till ye observe the Torah and the Gospel and that which was revealed unto you from your Lord. That which is revealed unto thee (Muhammad) from thy Lord is certain to increase the contumacy and disbelief of many of them. But grieve not for the disbelieving folk [5:68].
The second is that even if they did still exist without having been altered, the Quran has hegemony over them and abrogates acting according to them, And unto thee have We revealed the Scripture with the truth, confirming whatever Scripture was before it, and a watcher over it. So judge between them by that which Allah hath revealed, and follow not their desires away from the truth which hath come unto thee [5:48]; Follow that which is inspired in thee from thy Lord; there is no God save Him; and turn away from the idolaters [6:106]; And this is a blessed Scripture which We have revealed. So follow it and ward off (evil), that ye may find mercy [6:155]; (Saying): Follow that which is sent down unto you from your Lord, and follow no protecting friends beside Him. Little do ye recollect! [7:3].
Based on the preceding we can summarize that Muslims believe in the divinely revealed books in general, and particularly we believe that those that have been mentioned in the sources of our tradition were revealed to those specific prophets. Muslims do not, however, follow these books due to the reasons mentioned above. Muslims believe in the Quran and follow it because it is the final word of God to humanity; there is nothing that will abrogate or respond to it. And all Praise is to God Lord of the Worlds, and God is most high and knows best.