Mbh 13.50.2a

"'Bhishma said, "I shall, in this connection, O thou of great effulgence, recite to thee an ancient narrative of a conversation between Nahusha and the Rishi Chyavana. In days of yore O Chief of Bharata's race, the great Rishi Chyavana of Bhrigu's race, always observant of high vows, became desirous of leading for some time the mode of life called Udavasa and set himself to commence it. Casting off pride and wrath and joy and grief, the ascetic, pledging himself to observe that vow, set himself to live for twelve years according to the rules of Udavasa. The Rishi inspired all creatures with a happy trust. And he inspired similar confidence in all creatures living in water. The puissant ascetic resembled the Moon himself in his behaviour to all. Bowing unto all the deities and having cleansed himself of all sins, he entered the water at the confluence of the Ganga and the Yamuna, and stood there like an inanimate post of wood. Placing his head against it, he bore the fierce and roaring current of the two streams united together,--the current whose speed resembled that of the wind itself. The Ganga and the Yamuna, however, and the other streams and lakes, whose waters unite together at the confluence at Prayaga, instead of afflicting the Rishi, went past him (to show him respect). Assuming the attitude of a wooden post, the great Muni sometimes laid himself down in the water and slept at ease. And sometimes, O chief of Bharata's race, the intelligent sage stood in an erect posture. He became quite agreeable unto all creatures living in water. Without the least fear, all these used to smell the Rishi's lips. In this way, the Rishi passed a long time at that grand confluence of waters. One day some fishermen came there. With nets in their hands, O thou of great effulgence, those men came to that spot where the Rishi was. They were many in number and all of them were bent upon catching fish.