Short answer
Muslims believe in all the books Allah revealed. The Quran names the Scrolls (Suhuf) of Ibrahim and Musa, the Torah (Tawrat) given to Musa, the Psalms (Zabur) given to Dawud, the Gospel (Injil) given to Isa, and the Quran given to Muhammad ﷺ. The Quran is the final book and the only one preserved exactly as it was revealed.
Belief in Allah's revealed books is one of the six articles of faith. Muslims believe in the named books by name and in any others in general. The earlier books were sent to particular peoples; the Quran is for all people, confirms what was true in them and is now the binding guidance.
The four schools agree on this.
Explanation
When Jibril asked the Prophet ﷺ about faith, he answered: to believe in Allah, His angels, His books, His messengers, the Last Day, and the decree. The Quran says the Messenger and the believers "have believed in Allah and His angels and His books and His messengers" (2:285), and warns that whoever disbelieves in His books has gone far astray (4:136).
The books named in the Quran are these. The Suhuf, "the scriptures of Abraham and Moses" (87:19). The Tawrat, revealed to Musa. The Zabur: "to David We gave the book" (4:163). The Injil, given to Isa. And the Quran, revealed to Muhammad ﷺ over about twenty-three years. People often speak of "the four holy books", meaning the Torah, Psalms, Gospel and Quran, with the Scrolls as a fifth.
Muslims believe each of these was true revelation when it was sent. The earlier books were entrusted to their peoples, and over time their texts were changed or lost. The Quran is different: Allah took its protection upon Himself, "Indeed, it is We who sent down the Qur'an and indeed, We will be its guardian" (15:9). That is why the Quran is the criterion by which Muslims read everything else.
Read more in the six articles of faith, What is the Quran?, do Muslims believe in the Torah? and do Muslims believe in the Gospel?
The evidence
Quran, Surah An-Nisaa 4:136
يَٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوٓا۟ ءَامِنُوا۟ بِٱللَّهِ وَرَسُولِهِۦ وَٱلْكِتَٰبِ ٱلَّذِى نَزَّلَ عَلَىٰ رَسُولِهِۦ وَٱلْكِتَٰبِ ٱلَّذِىٓ أَنزَلَ مِن قَبْلُ ۚ وَمَن يَكْفُرْ بِٱللَّهِ وَمَلَٰٓئِكَتِهِۦ وَكُتُبِهِۦ وَرُسُلِهِۦ وَٱلْيَوْمِ ٱلْءَاخِرِ فَقَدْ ضَلَّ ضَلَٰلًۢا بَعِيدًا ﴿١٣٦﴾
O you who have believed, believe in Allah and His Messenger and the Book that He sent down upon His Messenger and the Scripture which He sent down before. And whoever disbelieves in Allah, His angels, His books, His messengers, and the Last Day has certainly gone far astray.
Commands belief in the Quran and the scriptures before it.
Quran, Surah Al-A'laa 87:19
صُحُفِ إِبْرَٰهِيمَ وَمُوسَىٰ ﴿١٩﴾
The scriptures of Abraham and Moses.
Names the Scrolls of Ibrahim and Musa.
Quran, Surah Al-Hijr 15:9
إِنَّا نَحْنُ نَزَّلْنَا ٱلذِّكْرَ وَإِنَّا لَهُۥ لَحَٰفِظُونَ ﴿٩﴾
Indeed, it is We who sent down the Qur'an and indeed, We will be its guardian.
Shows the Quran alone is protected from change.
Sahih Muslim 8
Sahih... أَنْ تُؤْمِنَ بِاللَّهِ وَمَلاَئِكَتِهِ وَكُتُبِهِ وَرُسُلِهِ وَالْيَوْمِ الآخِرِ ...
"That you believe in Allah, His angels, His books, His messengers and the Last Day."
Makes belief in the revealed books part of iman.
Where the ruling is recorded
- al-Aqida al-Tahawiyya, Section on belief in the angels, prophets and books. States belief in the books revealed to the messengers.
- al-Aqa'id al-Nasafiyya with Sharh al-Taftazani, Section on the revealed books. Affirms that Allah revealed books to His prophets, with commands, prohibitions, promises and warnings.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.