What is the difference between "those who were given the Scripture," "the disbelievers," and "the People of the Book" in the verse: "O you who have believed, take not as allies those who took your religion in ridicule and amusement from among those who were given the Scripture before you and the disbelievers, and fear Allah if you should be believers"?

The People of the Book are those who were given a scripture, such as the Jews and Christians. As for the disbelievers (kuffar), they are a broader category than the People of the Book, for every person from the People of the Book is a disbeliever, but not every disbeliever is from the People of the Book. The verses of the Qur'an indicate the inclusion of the People of the Book among the disbelievers. Scholars have differed regarding those who believe in the Psalms (Zabur) and the scriptures of Abraham, but are not Jews or Christians, as to whether they are considered among the People of the Book: The Hanafis hold that they are included, while the majority of jurists believe that the People of the Book are only Jews and Christians, citing the Almighty's saying: "Lest you say: 'The Scripture was sent down only to two groups before us'," and that the scriptures of Abraham and David contained admonitions and no rulings.