Question:
Since Allah sent messengers to all the people and no one was left without guidance does that not make all the people Ahlul Kitab?
Answer:
The Qur’an, the Prophet (s), the early Muslims and the consensus of the Umma applies the term Ahl al-Kitab to the Jews and the Christians, and to a more limited extent to the Zoroastrians, which qualifiedly (i.e. provided certain criteria are met) allows for the inclusion of other denominations. However, earlier pure-monotheistic dispensations might have continued to exist up to the Prophet’s time whether in pure form or in corrupted form, the latter being the basis for the Ahl al-Fatra, i.e. “people living in intervals” between Prophets. So not all non-Muslims are automatically Ahl al-Kitab.
Also, the premise that “no one was left without guidance” must be qualified in light of the last Message. Namely, the fact that the mission of the Seal of Prophets (Sayyidina Muhammad, upon him blessings and peace) supersedes and abrogates all other dispensations and Messages; and, furthermore, that no Prophet or Messenger other than him (s) was sent to the entirety of human beings. These givens, together with his hadith “Convey on my behalf, if only a single Aya,” establish that the conveyance of the message of guidance to all the people is a perpetual work in progress on the part of all Muslims until the Resurrection, and that there was never a moment in time when that work was completed. And Allah knows best.
Hajj Gibril Haddad