According to a well-known hadith, cleanliness and purity are half of the faith. It is obligatory for a Muslim to be clean and in a state of purity in order to offer formal prayer and recite the Quran by way of ablution, a ritual shower, or dry ablution. Purity and cleanliness encompass both physical and spiritual aspects. Physical impurities can be removed by clean, pure water or dry, clean earth or stone, and this is a beginning step for spiritual cleanliness. In the Purity of the Muslim, Saeed al-Qahtani explains in a clear and comprehensive manner the types of various impurities and the ways to attain purity and cleanliness according to the teachings of the Quran and of the final prophet, Muhammad (blessings and peace of Allah be upon him).