What a Muslim believes
Where the Five Pillars describe what a Muslim does, the Six Articles of Faith describe what a Muslim believes. In mainstream Sunni Islam these six articles together make up iman — inner faith.678 They are named in the narration in which the angel Jibril (Gabriel) asked the Prophet ﷺ about faith:
"[Faith is] that you believe in Allah, His angels, His Books, His Messengers, the Last Day, and that you believe in divine decree (qadar), both its good and its evil."
— Sahih Muslim 81
The Quran lists most of these articles together in a single verse:
"Whoever disbelieves in Allah, His angels, His books, His messengers, and the Last Day has certainly gone far astray."
— Quran 4:136 (Saheeh International)3
1. Belief in God (Allah)
The first and greatest article is belief in the one God — unique, eternal, and without partner. The believers are described as those who have "believed in Allah":
"All of them have believed in Allah and His angels and His books and His messengers."
— Quran 2:285 (Saheeh International)2
2. Belief in the angels
Muslims believe in angels as creations of God who carry out His commands — among them Jibril, who brought the revelation. Belief in the angels is named in the same verse above.2
3. Belief in the revealed Books
God sent revealed scriptures to guide humanity, including the Torah given to Moses and the Gospel given to Jesus, completed by the Quran:
"And He revealed the Torah and the Gospel."
— Quran 3:3 (Saheeh International)4
4. Belief in the Prophets and Messengers
Muslims believe God sent prophets and messengers to every people, from Adam through to the final Messenger, Muhammad ﷺ. Belief in "His messengers" is part of the faith of the believers.3
5. Belief in the Last Day
Muslims believe in the Day of Judgment, when all people will be resurrected and held accountable for their deeds. Denying the Last Day is named as a departure from faith in the verse above.3
6. Belief in divine decree (Qadar)
The sixth article is belief in divine decree — that God has knowledge and authority over all that happens, and that nothing occurs outside His will:
"Indeed, all things We created with predestination (a measure)."
— Quran 54:49 (Saheeh International)5
In short
The six articles of faith — belief in God, His angels, His books, His messengers, the Last Day, and divine decree — are the core of Islamic belief in the Sunni tradition. They define what is in a believer's heart, just as the Five Pillars define what is in a believer's practice.