Introduction to Kitab al-Iman: Book of Faith

Iman — faith — is the central reality of the Muslim life. But what exactly is iman? Is it merely verbal declaration? Inner belief of the heart? Action of the limbs? And can it increase and decrease? These questions, far from academic, determine how a Muslim understands their own spiritual state, the nature of sin, and the relationship between belief and deeds. They were among the most intensely debated questions in early Islamic theology, producing sharp divisions between the Khawarij, the Murji'ah, the Mu'tazilah, and Ahl us-Sunnah.

Kitab al-Iman by Shaykh al-Islam Ibn Taymiyyah (661–728 AH / 1263–1328 CE) is the definitive Athari Sunni treatment of this foundational question. Ibn Taymiyyah argues systematically — drawing on Quran, Sunnah, and the positions of the Companions and early scholars — that iman consists of three inseparable components: belief in the heart (tasdiq), speech of the tongue (iqrar), and action of the limbs ('amal). Iman is not a static state but increases through obedience and decreases through sin.

The work refutes the Murji'ah position (that deeds are irrelevant to iman) as well as the Khawarij position (that major sins expel one from Islam). Both extremes, Ibn Taymiyyah demonstrates, contradict the clear texts of the Quran and Sunnah and the consensus of the Salaf. The position of Ahl us-Sunnah occupies the middle ground: sin weakens iman, without necessarily destroying it.

As the authoritative Athari exposition of the theology of faith, Kitab al-Iman is essential reading for anyone seeking to understand Islamic aqeedah at its most rigorous and textually grounded level.