The Surprising Order of the Ayat:
Observe the order in this ayat, and you will find that it is not chronological. In the chronological sequence, the order would be “the ayat that were sent to people much before you i.e. Torah, Injeel, Zabur etc.” followed by “the ayat that have been sent to you i.e. Quran” followed by “conviction in the afterlife”. But Allah (subhanahu wa ta’ala) took the statement about the Quran and placed it at the beginning because he wants us to look at everything through the lens of the Quran. In other words, even when we are studying different religions, Quran should be our primary source, and all the previous books should be our secondary sources.
Rewards for Accepting Islam:
Reward for the People of the Book: The People of the Book (Jews and Christians) who embrace Islam and sincerely follow its teachings receive two rewards because they believe in both their previous scriptures and Islam. Others can only believe in general terms. The Prophet (sallallahu alaihi wasallam) advised that, “When the People of the Book narrate to you, neither reject nor affirm what they say. Rather, say, ‘We believe in what was revealed to us and what was revealed to you.’”
Equal Reward for Strong Faith: However, the faith that many Muslims have in Islam as it was revealed to Prophet Muhammad (sallallahu alaihi wasallam) might be more complete, encompassing and firmer than the faith of the People of the Book who embraced Islam. Therefore, if the believers in Islam among the People of the Book gain two rewards, other Muslims who have firmer Islamic faith might gain an equal reward that compares to the two the People of the Book gain (upon embracing Islam). And Allah knows best.
Hadith from Sahih Al-Bukhari and Sunan Abi Dawud
Narrated Abu Huraira (radi allahu anhu): The people of the Scripture (Jews) used to recite the Torah in Hebrew and they used to explain it in Arabic to the Muslims. On that Allah’s Messenger (sallallahu alaihi wasallam) said, “Do not believe the people of the Scripture or disbelieve them, but say: “We believe in Allah (subhanahu wa ta’ala) and what is revealed to us.”
Meaning
They are the kind of people who believe and are going to believe in what has been sent to you (Prophet Muhammad sallallahu alaihi wasallam) and what was sent to people much before you. And they have yaqeen (absolute conviction) in the afterlife.