This book presented in English garb, is Book III of the first quarter, namely, the Kitab Asrar al-Taharah (On the Mysteries of Purity). Though not one of the more profound contributions of al-Ghazali, it still remains an integral part of the Ihya' and should not, therefore, be neglected.

Regarding purity, it is mentioned in the Qur'an:

"Therein are men who aspire to purity, and God loveth the purified."

And the prophet said; "Purification is the key to prayer."

Purity has four stages: The first stage is the purification of the body from excrements, impurities, and bodily growths, and discharges. The second stage is the purification of the bodily senses from crimes and sins. The third stage is the purification of the heart from blameworthy traits and reprehensible vices. The forth stage is purification of the inmost self (sirr) from everything except Allah. This last stage is that of the Prophets and saints. This book address the first stage purity.