BELIEF IN THE BOOKS OF ALLAH
One must believe that Allah revealed Heavenly Books to His Messengers in order to convey them to mankind. These Books during their times contained nothing but the truth. All these Books call people to worship Allah alone, and that He is the Creator, Proprietor and Owner, and to Him belong the beautiful Attributes and Names.
Allah says: "Indeed We have sent Our Messengers with clear proofs, and revealed with them the Scripture and the Balance (justice) that mankind may keep up justice." Quran Surah 57:25
Different books revealed by Allah, mentioned in Qur’an are
Suhufe Ibraheem was the book revealed on Ibraheem. (Ibraheem) and Musa («Peace be upon them»): The scriptures of Abraham and Moses.Quran Surah A’la 87:19
The Torah is the Sacred Book which was revealed to Musa («Peace be upon him»). Allah says: "Verily, We did send down the Torah [to Musa], therein was guidance and light, by which the Prophets, who submitted themselves to Allah’s Will, judged the Jews. And the rabbis and the priests [too judged the Jews by the Torah after those Prophets] for to them was entrusted the protection of Allah’s Book, and they were witnesses thereto. Therefore fear not men but fear Me (O Jews) and sell not My Verses for a miserable price. And whosoever does not judge by what Allah has revealed, such are the disbelievers." Quran Surah Maidah 5:44
The Zaboor is the Book which was revealed to Dawood («Peace be upon him») (David). Allah says: "…and to Dawood We gave the Zaboor." Quran Surah Nisa 4:163
The Injeel is the Book which was revealed to ‘Eesaa («Peace be upon him») (Jesus, as few people called him). Allah says: "And in their footsteps, We sent ‘Eesaa, son of Maryam (Mary), confirming the Torah that had come before him. And We gave him the Injeel, in which was guidance and light and confirmation of the Tauraat (Torah) that had come before it, a guidance and an admonition for the Allah-fearing." Quran Surah Maidah 5:46
A Muslim must believe in all the Heavenly Books and he must believe that they are from Allah. It is not lawful for him to abide by its laws, since these Books were revealed to certain nations at certain times but whereas Quran was revealed for entire Mankind, Quran Surah Baqrah 2:185.
One must hold the following beliefs concerning it:
a. One must believe that the Qur'an is the Speech of Allah which Jibreel (Gabriel) («Peace be upon him») brought to Muhammadﷺin clear Arabic language. Allah says: "Which the trustworthy Rooh [Jibreel (Gabriel)] has brought down; * Upon your heart (O Muhammad) that you may be (one) of the warners, * In a plain Arabic language." (26:193-195)
b. One must believe that the Qur'an is the last of the Heavenly Books, which confirms the previous Books concerning the Message of Tawheed and the obligation to worship and obey Him. All previous Books were abrogated by the Qur'an. Allah says: "[It is] He Who has sent down the Book (the Qur'an) to you (Muhammad «peace be upon him») with truth, confirming what came before it. And he sent down the Torah and the Injeel. Aforetime, as a guidance to mankind, And He sent down the Furqaan (The Criterion) [of judgment between right and wrong (this Qur'an)]." Quran Surah 3:3-4
c. One must believe that the Qur'an contains all divine laws. Allah says: "This day, I have perfected your religion for you, completed My Favor upon you, and have chosen for you Islam as a religion." Quran Surah Midah 5:3
d. One must believe that it was revealed to mankind at large; not to a specific nation, as were previously revealed Heavenly Books. Allah says: "And We have not sent you [O Muhammad] except to all of humanity, as a giver of glad tidings and a warner, but most people know not." Quran Surah 34:28
e. One must believe that Allah has preserved the Qur'an from all distortions, adulterations, additions, or impairments. Allah says: "Indeed it is We ourselves Who have sent down the Remembrance (the Qur'an) and surely, it is We Who shall guard it [from distortion]." Quran Surah Hijr 15:9
"Those to whom We gave the Scripture [i.e. the Torah and the Injeel, etc.] before it, - they believe in it (the Qur'an). And when it is recited to them, they say: ‘We believe in it. Verily, it is the truth from our Lord. Indeed even before it we have been from those who submit themselves to Allah in Islam as Muslims (like ‘Abdullah bin Salaam and Salmaan Al-Faarisi, etc.). These will be given their reward twice over, because they are patient, and repel evil with good, and spend (in charity) out of what We have provided them." Quran Surah 28:52-54