Mbh 3.66.1b

And, O monarch, as long as he doth not leave thee, he will have to dwell in pain in thy body with thee every limb filled with my venom. And, O ruler of men I have saved from the hands of him who from anger and hate deceived thee, perfectly innocent though thou art and undeserving of wrong. And, O tiger among men, through my grace, thou shalt have (no longer) any fear from animals with fangs from enemies, and from Brahmanas also versed in the Vedas, O king! Nor shalt thou, O monarch, feel pain on account of my poison. And, O foremost of kings, thou shalt be ever victorious in battle. This very day, O prince, O lord of Nishadhas, go to the delightful city of Ayodhya, and present thyself before Rituparna skilled in gambling, saying, ‘I am a charioteer, Vahuka by name.’ And that king will give thee his skill in dice for thy knowledge of horses. Sprung from the line of Ikswaku, and possessed of prosperity, he will be thy friend. When thou wilt be an adept at dice, thou shalt then have prosperity. Thou wilt also meet with thy wife and thy children, and regain thy kingdom. I tell thee this truly. Therefore, let not thy mind be occupied by sorrow. And, O lord of men, when thou shouldst desire to behold thy proper form, thou shouldst remember me, and wear this garment. Upon wearing this, thou shalt get back thy own form.’ And saying this, that Naga then gave unto Nala two pieces of celestial cloth. And, O son of the Kuru race, having thus instructed Nala, and presented him with the attire, the king of snakes, O monarch, made himself invisible there and then!’”