Mbh 3.66.1a

“Vrihadaswa said, ‘O monarch, having deserted Damayanti, king Nala saw a mighty conflagration that was raging in that dense forest. And in the midst of that conflagration, he heard the voice of some creature, repeatedly crying aloud, ‘O righteous Nala, come hither.’ And answering, ‘Fear not,’ he entered into the midst of the fire and beheld a mighty Naga lying in coils. And the Naga with joined hands, and trembling, spake unto Nala, saying, ‘O king, that I am a snake, Karkotaka by name. I had deceived the great Rishi Narada of high ascetic merit, and by him have I been cursed in wrath, O king of men, even in words such as these: ‘Stay thou here like an immobile thing, until one Nala taketh thee hence. And, indeed, on the spot to which he will carry thee, there shalt thou he freed from my curse. It is for that curse of his that I am unable to stir one step. I will instruct thee in respect of thy welfare. It behoveth thee to deliver me. I will be thy friend. There is no snake equal to me. I will be light in thy hands. Taking me up, do thou speedily go hence.’ Having said this, that prince of snakes became as small as the thumb. And taking him up, Nala went to a spot free from fire. Having reached an open spot where there was no fire, Nala intended to drop the serpent, upon which Karkotaka again addressed him, saying, ‘O king of the Nishadhas, proceed thou yet, counting a few steps of thine; meanwhile, O mighty-armed one, I will do thee great good.’ And as Nala began to count his steps, the snake bit him at the tenth step. And, lo! As he was bit, his form speedily underwent a change. And beholding his change of form, Nala was amazed. And the king saw the snake also assume his own form. And the snake Karkotaka, comforting Nala, spake unto him, ‘I have deprived thee of thy beauty, so that people may not recognise thee. And, O Nala, he by whom thou hast been deceived and cast into distress, shall dwell in thee tortured by my venom.