An excerpt from Muhammad Asad’s Foreward:

One must beware of rendering, in each and every case, the religious terms used in the Qur'an in the sense which they have acquired after Islam had become “institutionalized” into a definite set of laws, tenets and practices. However legitimate this “institutionalization” may be in the context of Islamic religious history, it is obvious that the Qur'an cannot be correctly understood if we read it merely in the light of later ideological developments, losing sight of its original purport and the meaning which it had - and was intended to have - for the people who first heard it from the lips of the Prophet himself.

For instance, when his contemporaries heard the words islam and muslim, they understood them as denoting man’s “self-surrender to God” and “one who surrenders himself to God”, without limiting these terms to any specific community or denomination - e.g., in 3:67, where Abraham is spoken of as having “surrendered himself unto God” (kana musliman), or in 3:52, where the disciples of Jesus say, “Bear thou witness that we have surrendered ourselves unto God (bi-anna muslimun)”.

This makes so much sense to me. Oftentimes scholars will say that every Prophet was a Muslim, and the Adam was a Muslim, and that in the beginning all Jews and Christians were Muslims. And this wouldn’t make sense to me, logically.

In Arabic, this original meaning has remained unimpaired, and no Arab scholar has ever become oblivious of the wide connotation of these terms. Not so, however, the non-Arab of our day, believer and non-believer alike: to him, islam and muslim usually bear a restricted, historically circumscribed significance, and apply exclusively to the followers of the Prophet Muhammad. Similarly, the terms kufr (“denial of the truth”) and kafir (“one who denies the truth”) have become, in the conventional translations of the Qur'an, unwarrantably simplified into “unbelief” and “unbeliever” or “infidel”, respectively, and have thus been deprived of the wide spiritual meaning which the Qur'an gives to these terms; Another example is to be found in the conventional rendering of the word kitab, when applied to the Qur'an, as “book”: for, when the Qur'an was being revealed (and we must not forget that this process took twenty-three years), those who listened to its recitation did not conceive of it as a “book” - since it was compiled into one only some decades after the Prophet’s death but rather, in view of the derivation of the noun kitab from the verb kataba (“he wrote” or, tropically, “he as a "divine writ” or a “revelation”. The same holds true with regard to the Qur'anic use of this term in its connotation of earlier revealed scriptures: for the Qur'an often stresses the fact that those earlier instances of divine writ have largely been corrupted in the course of time, and that the extant holy “books” do not really represent the original revelations. Consequently, the translation of ahl al-kitab as “people of the book” is not very meaningful; in my opinion, the term should be rendered as “followers of earlier revelation”.