The Great Epic of the Bhārata dynasty 9.39.31

9.39.31

tathā vastrāṇyalaṃkāraṃ bhakṣyaṃ peyaṃ ca śobhanam |
adadānmudito rājanpūjayitvā dvijottamān || 31 ||

Vishvamitra, the son of Gadhi, however, regarding ascetic austerities highly efficacious, set his heart upon them. In this foremost of tirthas of the Sarasvati, O king, he began to emaciate his own body by means of vows and fasts with fixed resolve. He made water and air and (the fallen) leaves of trees his food. He slept on the bare ground, and observed other vows (enjoined for ascetics). The gods made repeated attempts for impeding him in the observance of his vows. His heart, however, never swerved from the vows (he had proposed to himself). Then, having practised diverse kinds of austerities with great devotion, the son of Gadhi became like the Sun himself in effulgence. The boon-giving Grandsire, of great energy, resolved to grant Vishvamitra, when he had become endued with ascetic merit, the boon the latter desired. The boon that Vishvamitra solicited was that he should be permitted to become a Brahmana. Brahma the Grandsire of all the worlds, said unto him, 'So be it.' Having by his austere penances acquired the status of Brahmanhood, the illustrious Vishvamitra, after the attainment of his wish, wandered over the whole Earth like a celestial. Giving away diverse kinds of wealth in that foremost of tirthas, Rama also cheerfully gave away milch cows and vehicles and beds, ornaments, and food and drink of the best kinds, O king, unto many foremost of Brahmanas, after having worshipped them duly.