Mbh 13.141.16a

"'"'The blessed and holy one said, "Yes, I shall recite to thee the high and excellent religion of the ascetics. By following the dictates of that religion, O auspicious lady, the ascetics attain to success through the severe penances they practise. O highly blessed one, do thou hear, from the beginning, what the duties are of those righteous Rishis that are conversant with every duty and that are known by the name of Phenapas. The Grandsire Brahma (during the days he devoted to the observance of penances) drank some nectar (in the form of water). That water had flowed in heaven from a great sacrifice. The froth of that water is highly auspicious and (in consequence of Brahma's having drunk it) it partook of His own nature. Those Rishis that subsist upon the measure of froth that thus issued (from the water indicated) are called Phenapas (Froth-eaters). Even this is the conduct of those pure-souled Rishis, O lady, possessed of wealth of penances! Listen now to me as I explain to thee who the Valkhilyas are. The Valkhilyas are ascetics that have won success by their penances. They reside in the solar disc. Adopting the means of subsistence that is followed by the birds, those Rishis, conversant with every duty of righteousness, live according to the Unchha mode. Their attire consists of deer-skins or barks of trees. Freed from every pair of opposites, the Valkhilyas, possessed of wealth of penances, walk in this track of righteousness. They are as big as a digit of the thumb. Distributed into classes, each class lives in the practice of the duties assigned to it. They desire only to practise penance. The merits they win by their righteous conduct are very high. They are regarded as having attained to an equality with the gods and exist for the accomplishment of the purposes of the gods. Having burnt off all their sins by severe penances, they blaze forth in effulgence, illuminating all the points of the compass.