If it is not purified, that evil prevents the benefits which the good in one's actions would provide. What is appropriate for the servant is first to abandon evil, and only then to seek the good. Purification from (evils) causes anxiety to the nafs (the lower self). For this reason, the nafs prefers to flee immediately to acts of obedience, as performing them without purification seems easier to it, due to the burden it feels from purification itself (because of this). (Ādāb, 76)
Tahāra (purification) is the cleansing of the qalb (the heart) from things such as rancor, envy, shirk (associating partners with God), and suspicion. Ṣafā (purity) is that which is free from any defect. Complete purification from all human qualities becomes constant, without change or alteration. However, this is not a quality of created beings, for Allah Most High is the One untouched by defects. Change is not conceivable in Allah. Created beings are tested by imtihān (trial); they are not free from defects and changes. They are subject to the rulings of servanthood. For this reason, they turn to Allah in tawba (repentance) and istighfār (seeking forgiveness). (Lumaʿ, 547)
Tatāhhur (purification) is the cleansing of the outward from impurities, and the cleansing of the inward from evil intentions, evil thoughts, and desires. (Taʿarruf, 7)
There are two kinds of tahāra: one is outward purification, and the other is inward (qalb) purification. Just as prayer is not valid without bodily purification, maʿrifa (gnosis, experiential knowledge of God) is not valid without purification of the qalb. Now, for bodily purification, mutlaq (pure) water is required. It is not permissible to purify with mixed, used, or impure water. For purification of the qalb, pure and sincere tawhid (the oneness of God) is necessary. A mixed and scattered creed is not suitable for this. (Hujwīrī, 345)
Tahāra (purification) is to cleanse the qalb from mā siwā (everything other than Allah). Wuḍūʾ (ritual ablution) is to cleanse the qalb from evil akhlāq (character traits) and vile desires. In prayer, (tahāra) is the qalb's upright orientation and attachment to the qibla of tawhid. Zakāt is to abstract and remove the qalb from the gains of income. In fasting, (tahāra) is fasting from mā siwā (everything other than Allah).