Something that isnt always conveyed clearly is how the Islam defines "other revelations" - We do beleive that Moses and Jesus received revealtions in the form of a book - as the Quran was revealed to Muhamed - however, this does not mean that the Torah today and the Bible today are those revealations - we concede that there may be parts of those books which are divine knowledge, but they have been cluttered and mixed with man made revealtions - so we dont know which is divine and which is not unless we compare it to the Quran - so if a passage in the bible agrees with the Quran - we can say that its divine - if it doesnt, we can only speculate on its origins. Heres an analogy - When Jesus was on earth - the Injeel, which was his revealtion was a clean bucket of water - then over the next 300 years - man began to drop impurities in that bucket - the impure parts and the clean parts are now indistinguishable - thus necesitating the need for a new, clean bucket of water - which was given to mankind in the form of the Quran.