In The Mysteries of Purification (Kitab asrar al-tahara), the third of the forty books of the Revival of the Religious Sciences (Ihyaʾ ʿulum al‐din), Abu Hamid al-Ghazali explains the fundamentals of the purification that is necessary in order to perform the five daily prayers. The book begins with an introduction to the general topic of purity. Imam al-Ghazali explains the hadith “Purification is half of faith,” and reminds readers that, for the earliest Muslims, inner purification was much more important than outer purification.
Each chapter includes a discussion of the Qur’anic verses, Hadith, and traditions from the Companions and the pious predecessors related to the subject at hand. Imam al-Ghazali then engages his readers in a heartfelt discourse; he offers proofs, metaphors, and examples to encourage seekers along the path to knowledge of the hereafter.