Purity (Pali: Vissudhi) is an important concept within much of Theravada and Mahayana Buddhism, although the implications of the resultant moral purification may be viewed differently in the varying traditions.
The aim is to purify the personality of the Buddhist practitioner so that all moral and character defilements and defects (kleśas such as anger, ignorance and lust) are wiped away and nirvana can be obtained.
So important is this notion of purity in Theravada Buddhism that the famed Buddhist monk and commentator Buddhaghosa composed a central thesis on dhamma called The Path of Purification (Visuddhimagga).
The Mahābherīharaka Sūtra elaborates that at the time one becomes a Tathāgata, one dwells in Nirvana and may be referred to as "permanent", "steadfast", "calm", "eternal" and "self" (ātman).
[2] The attainment of Buddhahood, resulting after eliminating the kleśas, is referred to in the Tathāgatagarbha literature and in the works of the Tibetan Jonangpa Lama Dolpopa as the "pure Self" (śuddha-ātman).