Bible Support From The Quran
(All quotes are from the New International Version of the Bible)
See 5 "Key Points" in Christians and The Quran for reasons why Muslims should trust the Bible.

Questions to ponder.
The Quran confirms the Bible.
We are to use the Bible to tell us if a revelation is from God.
The Torah is at least as good as Muhammad's judgment.
We have no ground to stand on without the Torah and Gospel.
The Torah makes things clear and the Gospel supports the Torah.
We are not allowed to believe in some scripture while rejecting others.
The true believers must believe in the Bible
You must believe in the Bible to have a firm faith in the afterlife.

Ask yourself the following questions:
If the Bible has been (or will be) corrupted why do we see the Quran supporting the Bible again and again?
How did God allow the Bible (a scripture in which we are required to believe, Sura 4:136) to be corrupted?
If the scripture has been corrupted, does this make the Quran "out of date" by telling us to read something that no longer exists (at least in pure form)?
Why did God give us the old scripture, then later contradict it with new scripture while at the same time having the new scripture tell us to read the former (contradictory) scripture?

The Quran confirms the Bible.
Suras 2:97, 2:101 and 6:92 all say that the Quran confirms the previous scriptures.

We are to use the Bible to tell us if a revelation is from God.
Sura 10:94  If you have any doubt regarding what is revealed to you from your Lord, then ask those who read the previous scripture.

The Torah is at least as good as Muhammad's judgment.
5:43  Why do they ask you (Muhammad) to judge among them (the Jews), when they have the Torah, containing GOD's law?

We have no ground to stand on without the Torah and Gospel.
Sura 5:68  O people of the scripture, you have no ground to stand on until you uphold the Torah, and the Gospel, and [the Quran].

The Torah makes things clear and the Gospel supports the Torah.
Sura 37:117  And We gave [Moses] the Book which helps to make things clear.

Sura 5:46  Subsequent to them, We sent Jesus, the son of Mary, confirming the previous scripture (the Torah).  We gave him the Gospel, containing guidance and light, and confirming the previous scriptures.

We are not allowed to believe in some scripture while rejecting others.
Sura 4:150-1 says that "the real disbelieves" are  (1)Those who disbelieve in GOD and His messengers [note the plural in messengers], (2) seek to make distinction among GOD and His messengers, (3) say, "We believe in some and reject some," and (4) wish to follow a path in between.

The true believers must believe in the Bible.
From Sura 5:44 to 5:47 the Quran talks about the Law (of Moses) and the Gospel (of Jesus).  Three times in this context the Quran says something like, "And whoever judges not by that which GOD has sent down, it is [they] who are the disbelieves".  The scripture that was "sent down" in these passages is not referring to the Quran for only after this (in 5:48) does the Quran talk about it's own roll to "confirm the previous scriptures", that being the Law and Gospel of which it was just talking about.

2:136  Say, We believe in GOD, and in what was sent down to us, and in what was sent down to Abraham, Ismail, Isaac, Jacob, and the Patriarchs and in what was given to Moses and Jesus, and all the prophets from their Lord. We make no distinction among any of them.  Also Sura 4:163  We gave David the Psalms.

Sura 3:93  Bring, then, the Torah and read it, if you are truthful.

4:136  O you who believe, you shall believe in GOD and His messenger, and the scripture He has revealed through His messenger, and the scripture He has revealed before that.

29:46  We believe in what was revealed to us and in what was revealed to you, and our God and your God is one and the same; to Him we are submitters.

5:47  the people of the Gospel shall rule in accordance with GOD's revelations therein. Those who do not rule in accordance with GOD's revelations are the wicked.

You must believe in the Bible to have a firm faith in the afterlife.
According to Sura 2:4 to have "firm faith in the hereafter" you must "believe in what was revealed to [Muhammad], and believe in what was revealed before [Muhammad]".