Vishnupurana 4.3.p5

4.3.p5

Accordingly Narmadā went to Purukutsa and led him to the regions below the earth, where, being filled with the energy of Vishnu he slew all the Gandharvas. He then returned to his own house. And the snake-gods conferred upon Narmadā a boon that whosoever should think of her, mention her name, should never have any fear from the snakes. This is the invocation: "Salutation unto Narmadā in the morning; salutation unto Narmadā at night, salutation to thee O Narmadā, save me from this serpent's poison". Whoever shall repeat this day and night shall not be bitten by a serpent in the dark or in entering a room. Nor shall he, who shall remember this, suffer from poison, when he eats even food mixed with it. They also conferred a boon on Purukutsa that none in this family shall be bitten.