I think with the Christians we have to make it clear from the beginning that the 'Injeel' revealed to 'Isa (Alayhi Salaam) does not even have a connection with the books of the New Testament at all, except for passing references to "Jesus preached the Gospel". With respect to the Bible in general, we can only say that those portions which are not blasphemous may have a divine origin, but we cannot even say that they are word-for-word of divine origin either, since there is no chain of transmission, the original books were lost and recovered, lost again and so forth.