Still waiting for our Muslim friends to answer why “they” believe it is corrupt?
My answer is for you to go read that book.
The reason Muslims beileve that the Bible is not purely the word of God, entirely revealed or inspired or preserved, but a hodgepodge of previous revelation mixed with other things… the reason Muslims believe that is:
3:77
As for those who sell the faith they owe to Allah and their own plighted word for a small price, they shall have no portion in the Hereafter: Nor will Allah (Deign to) speak to them or look at them on the Day of Judgment, nor will He cleans them (of sin): They shall have a grievous penalty.
3:78 There is among them a section who
distort the Book with their tongues: (As they read) you would think it is a part of the Book, but it is no part of the Book;
and they say, “That is from Allah,” but it is not from Allah: It is they who tell a lie against Allah, and (well) they know it!
5:13 But because of their [Children of Israel’s] breach of their covenant, We cursed them, and made their hearts grow hard;
they change the words from their (right) places and forget a good part of the message that was sent them, nor wilt thou cease to find them- barring a few - ever bent on (new) deceits: but forgive them, and overlook (their misdeeds): for Allah loveth those who are kind.
5:14 From those, too, who call themselves Christians, We did take a covenant,
but they forgot a good part of the message that was sent them: so we estranged them, with enmity and hatred between the one and the other, to the day of judgment. And soon will Allah show them what it is they have done.
2:91 When it is said to them, "Believe in what Allah Hath sent down, "they say, “We believe in what was sent down to us:” yet they reject all besides, even if it be Truth confirming what is with them. Say: “Why then have ye slain the prophets of Allah in times gone by, if ye did indeed believe?”
4:46 Of the Jews** there are those who displace words from their (right) places**, and say: “We hear and we disobey”; and “Hear what is not Heard”; and “Ra’ina”; with a twist of their tongues and a slander to Faith. If only they had said: “What hear and we obey”; and “Do hear”; and “Do look at us”; it would have been better for them, and more proper; but Allah hath cursed them for their Unbelief; and but few of them will believe.
5:41 O Messenger! let not those grieve thee, who race each other into unbelief: (whether it be) among those who say “We believe” with their lips but whose hearts have no faith; or it be among the Jews,-
men who will listen to any lie,- will listen even to others who have never so much as come to thee.** They change the words from their (right) times and places: they say, “If ye are given this, take it, but if not, beware!” **If any one’s trial is intended by Allah, thou hast no authority in the least for him against Allah. For such - it is not Allah’s will to purify their hearts. For them there is disgrace in this world, and in the Hereafter a heavy punishment.
2:174
Those who conceal Allah’s revelations in the Book, and purchase for them a miserable profit,- they swallow into themselves naught but Fire; Allah will not address them on the Day of Resurrection. Nor purify them: Grievous will be their penalty.
2:79
Then woe to those who write the Book with their own hands, and then say:“This is from Allah,” to traffic with it for miserable price!- Woe to them for what their hands do write, and for the gain they make thereby.
In other words, the Muslims believe it because the Qur’an says it.