This explaination can be found in the earlist stories of Creation.

Began back when the story of time was still a wet canvas awaiting the brushstrokes of desire. The gods (devi) and the demons formed a coalition to churn the milky ocean of creation so that they could bring forth all the treasures contained within.

Both were after the nectar of immortality and although both had agreed to share the spoils of their efforts, neither had any intention of doing so.

In order to churn the vast ocean of milk, the gods called up Mount Mandara, the cosmic mountain. Wrapping the sublime serpent Vasuki around the mountain they began to churn. But the weight of the mountain was too much for even the combined efforts of both the demons and the devi and it began to sink under the vast ocean. Suddenly Vishnu appeared in the form of the turtle, Kurma, and offered his back to support the mountain, and the churning began in earnest.

The first thing to emerge from the churning ocean was a hissing blue stream of gas and deadly poison called Halahala. This poison, a forerunner to the Bhopal Union Carbine disaster, threatened to suffocate every living thing. The gods began to choke and cough, while some of the demons fainted away. The limbs of Mother Nature began to curl and turn cancerous.

The poisonous gas curled into the nostrils of sleeping infants and toothless old men, every flower in creation began to wilt, and birds in the forest fell to earth like the dead leaves of autumn. Suddenly the great god Shiva appeared to save the situation and swallowed the vile concoction. But Parvatti, alarmed at the threat to her beloved, held her hands at his throat to stop the poison. Whispering tender endearments she named him her darling Nilankatha, meaning The One with the Blue Throat, as his white throat turned blue with the toxins.

Next, Surabhi, the sacred mother cow and giver of abundance rose into being.

So the cow is worshipped as the first and most blessed version of the gift of mother nature. She is the first and best example of motherhood and giving in Indian literature. Surabhi was followed by Kaustubha the celestial jewel that adorns Vishnu’s chest. Then came the white elephant, the divine celestial horse, the wish fulfilling divine tree and then on a wave of foam arose the most beautiful Laskhmi, floating on a lotus flower. Vishnu fell eternally in love and claimed her as his bride. Shiva took the moon that arose next and put it as a diadem in his hair.

Finally, Dhanvantari, the Heavenly Physician emerged holding a pot (Khumb) containing the nectar of immortality and both angels and demons stampeded in an overwhelming rush of desire.

As they wrestled between themselves for the nectar, four drops of the precious liquid fell to earth. One drop kissed the feet of the Himalaya before landing with a splash in the swirling waters of Ganga Goddess in Haridwar, another swirled into the mix where the three goddess rivers, Ganga, Yamuna and the mythical Saraswati meet at Allahabad, another glanced off the lingam of light that manifested in Ujjain on the shores of the Shipra River and the fourth landed with a plop in the Godavari River as she flowed past Nasik.

Suddenly it seemed that the demons would wrest the golden pot from the devi who were beginning to loose their grip. Vishnu appeared as Mohini, a ravishing beauty. The demons were so distracted by her loveliness that they dropped their jaws and the pot in open mouthed astonishment at her beauty. They stampeded again across the heavens in pursuit of this enchantingly unreal vision leaving the henceforth immortal angels the victors.

This celestial victory is celebrated today in the Khumba Mela festival.