Dhutanga (Pali dhutaṅga, ධුතාඞ්ග) or dhūtaguṇa (Sanskrit) is a group of austerities or ascetic practices taught in Buddhism. The Theravada tradition teaches a set of thirteen dhutangas, while Mahayana Buddhist sources teach a set of twelve dhūtaguṇas. The term is generally understood to be derived from the root dhu "to shake" and could mean practices which help one "shake off" the defilements. Thus, the dhutangas are meant help eliminate the defilements in the mind, and thus to deepen Buddhist practice. Their aim is to help the practitioner to develop detachment with material things including the body. Dhutanga practice is not considered a necessary requirement for a monk as is Śīla (virtue). As these thirteen ascetic practices are mentioned in the Pali Tipitaka merely by its name, the Visuddhimagga is considered the only place in the Theravada Literature where adequate descriptions on dhutangas are found. The Visuddhimagga, the central Theravada Buddhist commentary treatise, by highly revered 5th century monk Buddhaghosa Thera, sets out detailed practical instructions for developing purification of mind by devoting a whole chapter to discussing dhutangas. The Visuddhimagga lists the practices as follows: Thirteen kinds of ascetic practices have been allowed by the Blessed One to clansmen who have given up the things of the flesh and, regardless of body and life, are desirous of undertaking a practice in conformity [with their aim]. They are: Refuse-rag-wearer's Practice (pamsukulik'anga) — wearing robes made up from discarded or soiled cloth and not accepting and wearing ready-made robes offered by householders. Triple-robe-wearer's Practice (tecivarik'anga) — Having and wearing only three robes and not having additional allowable robes. Alms-food-eater's Practice (pindapatik'anga) — eating only food collected on pindapata or the almsround while not accepting food in the vihara or offered by invitation in a layman's house.