When you prepare for prayer, wash your faces...[Sahl] said:Purification consists of four things: purity of the source of food, truthfulness of the tongue, avoidance of all sins, and the humility in one’s innermost secret (sirr). In turn, each one of these four corresponds to the purification of the outer members of the body.His words, Exalted is He: …But He wishes to purify you...That is, to purify your state, your character and your actions, so that you return to Him in a state of true poverty (ḥaqīqat al-faqr) without being attached to any [secondary] cause.Purification is of seven kinds: the purification of knowledge from ignorance, the purification of remembrance from forgetfulness, the purification of obedience from disobedience, the purification of certainty from doubt, the purification of the intellect from foolishness, the purification of opinion from slander, and the purification of faith from anything which is alien to it. Furthermore, each punishment constitutes a kind of purification, except the punishment of the heart, which is hardness. [Concerning] His words, Exalted is He: