According to Quran, Muslims must believe in all the Divine books, and in all the prophets: آمَنَ الرَّسُولُ بِمَا أُنْزِلَ إِلَيْهِ مِنْ رَبِّهِ وَ الْمُؤْمِنُونَ كُلٌّ آمَنَ بِاللَّهِ وَ مَلَائِكَتِهِ وَ كُتُبِهِ وَ رُسُلِهِ لَا نُفَرِّقُ بَيْنَ أَحَدٍ مِنْ رُسُلِهِ ... [2:285] which is translated into The Messenger has believed in what was revealed to him from his Lord, and [so have] the believers. All of them have believed in Allah and His angels and His books and His messengers ....
But how? Is Bible a Divine book? Once I used to talk with some Christians, asking them about Enjil, and they said they have never heard about it, and that maybe we actually mean to say "Gospels". But Gospels are not divine, they are considered to be teachings of Jesus the Christ PBUH in the language of some of his companions PBUH. There is a Hadeeth from Imam Ridha PBUH in a debate with a Christian scholar, wherein Imam PBUH explained why Christians gatherings in Churches happen on Sundays instead of Saturday which was the day for Jews at those early times (and now). To make it short, after Jesus PBUH was risen up to the Heavens, Enjil (which like Turah and Dhabur was revealed as a single written book, and not like Quran which was revealed to the vocal level) was also lost, and his companions told people to gather every Sonday in a place to teach them what they knew of the book and what Jesus PBUH taught them. This became a tradition then after. According to Christian people, there were lots of Gospels, which at some point, were decided to be burned for only four books to be kept. Now there is also (at least) a fifth one called Barnabas' Gospel, which I have read personally due to advise of some great Shia scholars and its has very small deviation from the teachings of Islam, but is not considered very authenticate by most of the Christians. Barnabas was also among the companions of Jesus the Christ PBUH. What about the other Gospels? While discussing things with the Christians it appeared to me that If only Paul's advertising God in a flesh (i.e. Trinitarian) is put aside, the Christians will become true Unitarian. Interesting enough, (saint) Paul is considered the greatest enemy of Jesus PBUH at the prophet's time even by the Christians, who then (self-expressively) introduced himself a regretful repented person after Jesus PBUH, and deviated the Christians by withstanding in front of Saint Peter (شمعون صفا) which was the true successor of Jesus PBUH according to our Islamic teachings. Now Christians accept from Paul, a symbol of hypocrisy, and are sorry for Saint Peter not accepting from him, if I have got it right.
What about Torah? Torah had also an amazing story. Once, I personally conducted a research to some extent about how it has failed over the time, but couldn't find a hint in our Islamic teaching about the book being corrupted on its own. Even e.g. Torah was lost for a long time and another prophet Uzair PBUH (a story of him is in Quran) brought it back again to Jews, so that the book was left intact at least for centuries after Moses PBUH. I also had some conservation with some Jews and they had reasons for their book to have remained intact. Also Quran accuse the Jews not for corrupting their Divine book, but for misinterpretting the notions in their book.
فَبِمَا نَقْضِهِمْ مِيثَاقَهُمْ لَعَنَّاهُمْ وَ جَعَلْنَا قُلُوبَهُمْ
قَاسِيَةً يُحَرِّفُونَ الْكَلِمَ عَنْ مَوَاضِعِهِ وَ نَسُوا حَظًّا
مِمَّا ذُكِّرُوا بِهِ وَ لَا تَزَالُ تَطَّلِعُ عَلَيٰ خَائِنَةٍ
مِنْهُمْ إِلَّا قَلِيلًا مِنْهُمْ ... [5:13]
So for their breaking of the covenant We cursed them and made their
hearts hard. They distort words from their [proper] usages and have
forgotten a portion of that of which they were reminded. And you will
still observe deceit among them, except a few of them ...
This is also happening in Islam, as any scripture requires an ultimate interpreter which can judge who understand the message right, and who is misusing the same saying for its own (wrong) benefits. There are several verses in Quran and several Hadeeth about this issue, and that's why there is one book Quran among Muslims which is the same in Saudi-Arabia, Iran, Yemen, Egypt, and all over the globe, but with several different understanding from it. Here I only grab your attention to some verses and Ahadeeth about the issue:
وَ مَا أَنْزَلْنَا عَلَيْكَ الْكِتَابَ إِلَّا لِتُبَيِّنَ لَهُمُ
الَّذِي اخْتَلَفُوا فِيهِ وَ هُدًي وَ رَحْمَةً لِقَوْمٍ يُؤْمِنُونَ
[16:64]
And We have not revealed to you the Book, [O Muhammad], except for
you to make clear to them that wherein they have differed and as
guidance and mercy for a people who believe
هُوَ الَّذِي أَنْزَلَ عَلَيْكَ الْكِتَابَ مِنْهُ آيَاتٌ مُحْكَمَاتٌ
هُنَّ أُمُّ الْكِتَابِ وَ أُخَرُ مُتَشَابِهَاتٌ فَأَمَّا الَّذِينَ فِي
قُلُوبِهِمْ زَيْغٌ فَيَتَّبِعُونَ مَا تَشَابَهَ مِنْهُ ابْتِغَاءَ
الْفِتْنَةِ وَ ابْتِغَاءَ تَأْوِيلِهِ وَ مَا يَعْلَمُ تَأْوِيلَهُ
إِلَّا اللَّهُ وَ الرَّاسِخُونَ فِي الْعِلْمِ يَقُولُونَ آمَنَّا بِهِ
كُلٌّ مِنْ عِنْدِ رَبِّنَا وَ مَا يَذَّكَّرُ إِلَّا أُولُوا
الْأَلْبَابِ [3:7]
It is He who has sent down to you, [O Muhammad], the Book; in it are
verses [that are] precise - they are the foundation of the Book -
and others unspecific. As for those in whose hearts is deviation [from truth], they will follow that of it which is unspecific, seeking
discord and seeking an interpretation [suitable to them]. And no one
knows its [true] interpretation except Allah, and those firm in
knowledge; [they] say, 'We believe in it. All [of it] is from our
Lord.' And no one will be reminded except those of understanding.
قال رسول الله صلیاللهعلیهوآله: ...إِنِّی تَارِکٌ فِیکمْ أَمْرَینِ
إِنْ أَخَذْتُمْ بِهِمَا لَنْ تَضِلُّوا: کِتَابَ اللَّهِ عَزَّ وَ جَلَّ
وَ أَهْلَ بَیتِی عِتْرَتِی. أَیُّهَا النَّاسُ اسْمَعُوا وَ قَدْ
بَلَّغْتُ إِنَّکُمْ سَتَرِدُونَ عَلَیَّ الْحَوْضَ فَأَسْأَلُکُمْ
عَمَّا فَعَلْتُمْ فِی الثَّقَلَیْنِ، وَ الثَّقَلَانِ کِتَابُ اللَّهِ
جَلَّ ذِکْرُهُ وَ أَهْلُ بَیتِی فَلَا تَسْبِقُوهُمْ فَتَهْلِکُوا وَ
لَاتُعَلِّمُوهُمْ فَإِنَّهُمْ أَعْلَمُ مِنْکُم
The Messenger of God, may God’s prayers and peace be upon him and his
family, said: ...I am leaving with you two matters, which if you
follow them you will never go astray: The Book of God Almighty and My
Household. O people, listen, and I have been informed that you will
return to the Fountain (Al-Kawthar), so I will ask you about what you
did regarding the Thaqalayn, and the Thaqalayn is the Book of God,
glory be to Him And my household, do not outpace them or you will be
destroyed, and do not teach them, for they are more knowledgeable than
you.
The latter Hadeeth is more-or-less repeated several times in Shia and Sunni authenticate books with sometimes small differences. So that the slogan "حَسْبُنا کِتابَ الله" (that is, The Book of God is sufficient for us) which was used in the beginning of the history of Islam, was indeed opposing both Quran and Hadeeth. And Jews suffered from the same corruptions. Allah AWJ hold a mountain over the head of a group of selected Israelite and they were asked to say the truth, but they preferred to break their covenant.
وَ إِذْ أَخَذْنَا مِيثَاقَكُمْ وَ رَفَعْنَا فَوْقَكُمُ الطُّورَ خُذُوا
مَا آتَيْنَاكُمْ بِقُوَّةٍ وَ اذْكُرُوا مَا فِيهِ لَعَلَّكُمْ
تَتَّقُونَ
And [recall] when We took your covenant, [O Children of Israel, to
abide by the Torah] and We raised over you the mount, [saying], 'Take
what We have given you with determination and remember what is in it
that perhaps you may become righteous.'
وَ إِذْ أَخَذْنَا مِيثَاقَكُمْ وَ رَفَعْنَا فَوْقَكُمُ الطُّورَ خُذُوا
مَا آتَيْنَاكُمْ بِقُوَّةٍ وَ اسْمَعُوا، قَالُوا سَمِعْنَا وَ
عَصَيْنَا! وَ أُشْرِبُوا فِي قُلُوبِهِمُ الْعِجْلَ بِكُفْرِهِمْ، قُلْ
بِئْسَمَا يَأْمُرُكُمْ بِهِ إِيمَانُكُمْ إِنْ كُنْتُمْ مُؤْمِنِينَ
And [recall] when We took your covenant and raised over you the mount,
[saying], 'Take what We have given you with determination and listen.'
They said [instead], 'We hear and disobey.' And their hearts absorbed
[the worship of] the calf because of their disbelief. Say, 'How
wretched is that which your faith enjoins upon you, if you should be
believers.'
they followed their desires except a small group of them, and so did Muslims at the early Islamic era. There is a Hadeeth about it from the holy prophet PBUHH:
فقد ثبت في الحديث الصحيح أن النبي صلى الله عليه و آله قال: افترقت
اليهود على إحدى وسبعين فرقة، وافترقت النصارى على اثنتين وسبعين فرقة،
وستفترق هذه الأمة على ثلاث وسبعين فرقة كلها في النار إلا واحدة
It has been proven in the authentic hadith that the Prophet, may God
bless him and his household, said: The Jews split into seventy-one
sects, and the Christians split into seventy-two sects, and this
nation will split into seventy-three sects, all of whom will be in
Hell except one.
and we already know all Muslims follow a single intact book, Quran. So that, for a people to deviate from the truth, it is not always required for their book of instructions to be lost, or be changed with bad intentions, but they can always misuse their book, like Jews that said سَمِعْنَا وَ عَصَيْنَا. Apparently, Jew have some books beside Torah which they obey much and many of their corrupted beliefs are due to those books, written trough centuries by their Rabbis.
And what about Dhabur of the prophet David PBUH? There is a book in Old Testimonials which is considered to be from David PBUH, but there are doubts around it, and I have not conducted any research in this regard, so only a hint for you to do so ...
