Vishnupurana 5.7.8

5.7.8

tad asya nāgarājasya kartavyo nigraho mayā
ciram atra sukhaṃ yena careyur vrajavāsinaḥ //

ONE day Krishńa, unaccompanied by Ráma, went to Vrindavan: he was attended by a troop of cowherds, and gaily decorated with wild flowers. On his way he came to the Yamuná, which was flowing in sportive undulations, and sparkling with foam, as if with smiles, as the waves dashed against the borders. Within its bed, however, was the fearful pool of the serpent Kálíya, boiling with the fires of poison; from the fumes of which, large trees upon the bank were blighted, and by whose waters, when raised by a gale into the air, birds were scorched. Beholding this dreadful lake, which was like another mouth of death, Madhusúdana reflected that the wicked and poisonous Kálíya, who had been vanquished by himself (in the person of Garud́a), and had been obliged to fly from the ocean (where he had inhabited the island Ramańaka), must be lurking at its bottom, and defiling the Yamuná, the consort of the sea, so that neither men nor cattle could slake their thirst by her waters. Such being the case, he determined to dislodge the Nága, and enable the dwellers of Vraja to frequent the vicinage without fear; for it was the especial purpose he considered of his descent upon earth to reduce to subjection all such violators of law. "Here," thought he, "is a Kadamba tree, which is sufficiently near; I can climb up it, and thence leap into the serpent's pool." Having thus resolved, he bound his clothes tightly about him, and jumped boldly into the lake of the serpent-king.