The Christians opine that:
Muhammad [Propeht, pbuh] lived between the years 570 and 632.
The entire New Testament as we know it today, was canonized around 375 A.D.
"...the major writings were accepted by almost all Christians by the middle of the second century, and by the fifth century the East, with a few exceptions, had come to accept the Book of Revelation and thus had come into harmony on the matter of the canon."
And the Quran states the following:
Sura 5:68 (Al-Maida) - "Say: 'People of the Book (Christians and Jews), you stand for nothing until you observe the Torah and the Gospel and that which is revealed to you from your Lord."
Sura 4:136 (Al-Nisa) - "0 believers, have faith in Allah and His Apostle, in the Book He has revealed to His Apostle, and in the Book He formerly revealed (Bible). He that denies Allah, His angels, His Scriptures, His apostles, and the Last Day, has strayed far from the truth."
Sura 5:48 (Al-Maida) - "And to you We have revealed the Book with the truth confirming what was revealed before it in the other Books, and standing as a guardian over it."
Response / Comments:
The verses are too long to post altogether, but a few of those which suggest previous scriptures/books were corrupted are the following: 5:13, 5:15, 5:41, 2:159, 2:174, 3:75, 3:187, 4:46, 7:162, etc.
The verses you posted above suggest that the People of the Book (Jews, Christians, Sabians) are to follow Muhammad (pbuh).
Verse 5:68 of the Holy Quran:
"Say, "O People of the Scripture, you are [standing] on nothing until you uphold the Torah, the Gospel, and what has been revealed to you from your Lord." And that which has been revealed to you from your Lord will surely increase many of them in transgression and disbelief. So do not grieve over the disbelieving people."
- The verse is clear that they stand for nothing "until you uphold the Torah, the Gospel, and what has been revealed to you from your Lord." That means the Torah, the Gospel, AND what has been revealed to you (Quran).
Verse 4:136 of the Holy Quran:
"O you who have believed, believe in Allah and His Messenger and the Book that He sent down upon His Messenger and the Scripture which He sent down before. And whoever disbelieves in Allah, His angels, His books, His messengers, and the Last Day has certainly gone far astray."
- The People of the Scripture must "believe in Allah and His Messenger and the Book that He sent down upon His Messenger and the Scripture which He sent down before"
Verse 5:48 of the Holy Quran:
"And We have revealed to you, [O Muhammad], the Book in truth, confirming that which preceded it of the Scripture and as a criterion/guardian over it. So judge between them by what Allah has revealed and do not follow their inclinations away from what has come to you of the truth..."
Now comes the issue of those who follow the Torah and the Gospel. If they had upheld the Scriptures in truth, the would also believe in the Quran and in Muhammad (pbuh):
"Those who follow the Messenger, the unlettered prophet, whom they find written in what they have of the Torah and the Gospel, who enjoins upon them what is right and forbids them what is wrong and makes lawful for them the good things and prohibits for them the evil and relieves them of their burden and the shackles which were upon them. So they who have believed in him, honored him, supported him and followed the light which was sent down with him it is those who will be the successful." The Holy Quran - 7:157
The only Books/Scriptures considered to be Holy are the Scrolls of Abraham and Moses, the Torah of Moses, the Psalms of David, the Gospel of Jesus, and the Quran of Muhammad (pbut). Each of these constitute "parts" of the complete revelation from Allah (swt) of the "Mother of the Book", also referred to as "Louh Al-Mahfouth". The Quran is the last revelation sent by Allah (swt):
"And We have revealed to you, [O Muhammad], the Book in truth, confirming that which preceded it of the Scripture and as a criterion/guardian over it."
The Quran suggests that the previous Scriptures/Books were in fact corrupted, but does not clarify in what aspect. What we do no for a fact is that they were corrupt and that the Quran "confirms it in truth and as a criterion/guardian over them".
The issue now comes with the fact that the Christians follow the Bible, not the Gospel itself. Why only the Gospels of Mark, Matthew, Luke, and John? Why not the Gospel of Barnabas? The Christians worship three parts on a God, claiming it as one. This is views as complete polytheism and idolatry. And on top of that, the scriptures/ books according to the Quran are indeed corrupt.