Narada Parivrajaka Upanishad of Atharvaveda, Chapter VII

The Grandfather, after eulogizing Nārada who asked about the observance of ascetics, replied thus:—

"The ascetic that has attained indifference (to objects), should stay in one and the same place in the rainy season (for four months), and then for (the remaining) eight months should wander alone. Then also the ascetic should not stay in one and the same place for more than a day. Like a deer that does not stay in one place on account of fear, he should not stay in one place. He should not create an attraction (in his mind) that may serve as an obstacle to his going about. He should not cross a stream (by swimming) with his hand, nor ascend a tree, nor witness the festival of a God, nor partake of regal food, nor do the external worship of God. Having discarded all things other than the Self, he should be with his body emaciated by taking food (from each house) like the bees (from each flower). He should not increase the fat (in the body); he should discard ghee like blood. Regarding such royal food as flesh, sandal-coating, etc., as offal, the different tastes as the degraded caste, the cloth as a defiled vessel, the oil-bath as sexual union, the gladdening of a friend as urine, desires as cow's flesh, the country known to him as the outcastes’ place, gold and women as cobra or deadly poison, the place of assembly as the burning ground, the capital of the town as the hell called Kumbhīpāka, and royal food as balls of rice offered to the dead, he should be without any worship of God other than the Self; and having given up all the actions of the world and his own country, and ever thinking of the bliss of his Self like the bliss arising from the discovery of a lost object, forgetting his country and the fondness for his body, and knowing that his body should be slighted like a carcase, he should dwell away from son, relations and native place, like a thief released from prison. Taking whatever comes to him without effort, ever intent upon the realisation, through meditation, of Brahma-Praṇava, being freed from all karmas, having burnt up all passion, anger, greed, delusion, pride, malice, etc., having transcended the three guṇas, being without the six human infirmities,^[1] without the six changes,^[2] speaking the truth and being opposed to all savoury things, he should live for one day in a village, five days in a town, five days in a sacred place, and five days in sacred waters. With no settled place of residence and with a firm mind, he should dwell alone in mountain caves without uttering falsehood. Two persons should not join together. Should three join, there is created a village thereby; with four, is formed a city. Therefore he should live alone in a village. In it, the ascetic should not give scope to his fourteen organs. Having attained wealth of vairāgya through the non-dissipated jñāna, and having deliberated within himself that there is none other than the Self, he should attain Jīvanmukti, having seen the Reality everywhere. Till prārabdha karma is over, he should understand the four kinds of svarūpa^[3] (in Tattvamasi) and should live in the realisation of Reality, till his body falls (a prey to death).

"To the kutīcaka there is (prescribed) a bath three times daily; to the bahūdaka, twice; to the haṃsa, once; to the paramahaṃsa there is the mental bath; to the turyātīta, there is the holy-ashes bath; to the avadhūta, there is the wind as the bath. For the kutīcaka, there is the vertical sect-mark; for the bahūdaka, there is the three-lined (horizontal) sect-mark; for the haṃsa, both; for the paramahaṃsa, there is the holy-ashes sect-mark; for the turyātīta, there is the spot-sect-mark; for the avadhūta or for the turyātīta and avadhūta, there is none. For the kutīcaka, shaving takes place once in two months; for the bahūdaka, once in four months; for the haṃsa and paramahaṃsa, none, or if wanted, once in a year; for the turyātīta and avadhūta, none at all. The kutīcaka should take the food in one (place only); the bahūdaka should take alms (in many places); for the haṃsa and paramahaṃsa, the hand is the vessel; the turyātīta, should take food with the mouth as the cow; for the avadhūta, it is like the action of the boa constrictor (opening the mouth and taking whatever comes into it). For the kutīcaka, there are two cloths; for the bahūdaka, there is one cloth; for the haṃsa there is a piece of cloth; and the paramahaṃsa should be naked or have only a loin-cloth; in the case of the turyātīta and avadhūta, they should be as nature made them. For the haṃsa and paramahaṃsa, there is (prescribed) a deerskin, and for no others. For the kutīcaka and bahūdaka, there is the worship of the divine (image); for the haṃsa and paramahaṃsa, there is mental worship; for the turyātīta and avadhūta, there is the idea that they alone are Brahman. The kutīcaka and bahūdaka are entitled to mantras and japas; the haṃsa and paramahaṃsa, to dhyāna (meditation); the turyātīta and avadhūta are entitled to none; but they are entitled to the initiation of the sacred sentences of the Vedas; so also the paramahaṃsa. The kutīcaka and bahūdaka are not entitled to initiate others; for them, there is (the uttering of) the mental praṇava; for the haṃsa and paramahaṃsa, there is the internal praṇava (in the heart); for the turyātīta and avadhūta, there is the Brahma-praṇava (always). For the kutīcaka and bahūdaka, there is śravaṇa (hearing and study); for the haṃsa and paramahaṃsa, there is manana (thinking and remembering); for the turyātīta and avadhūta there is nididhyāsana (profound meditation ever). For all these, there is necessarily the meditation upon Ātmā. Thus the aspirant after salvation should ever be uttering the Praṇava which enables one to cross saṃsāra, and be living as a Jivanmukta. Thus the ascetic, according to each one's capacity, should ever be seeking the means to attain Kaivalya. Such is the Upaniṣad."