Bhagiratha's Austerities and Ganga's Appearance
For a thousand celestial years, King Bhagiratha lives on nothing but fruits, roots, and water, performing terrible austerities to bring the river Ganga down from heaven. When she finally appears in personified form and asks what he desires, he tells her the story of his grandfathers — the sixty thousand sons of Sagara, destroyed by the sage Kapila, whose ashes cannot reach heaven without being touched by her waters. Ganga agrees to descend, but warns him that no one in the three worlds can withstand her force except Nilakantha Maheshvara himself.
Bhagiratha was the best of men, and he undertook a task that would have broken anyone else.
He went to the Himalayas and began to perform austerities — terrible austerities, the kind that strip a man down to his bones. For a thousand celestial years he lived on nothing but fruits, roots, and water. He did not move from his spot. He did not waver. His entire being was focused on one thing: bringing Ganga, the great river of heaven, down to earth.
A thousand celestial years passed.
Then Ganga appeared before him in personified form — the daughter of the Himalayas, the river that flows through the sky, worshipped by all the worlds. She asked him what he wanted.
Bhagiratha told her.
His grandfathers were the sixty thousand sons of Sagara, a king of the solar dynasty. Sagara had performed the ashvamedha (horse sacrifice), and the sacrificial horse had been stolen. He sent his sixty thousand sons to find it. They searched the earth, digging through its depths, until they reached the underworld where the sage Kapila sat in meditation. They mistook him for the thief. They attacked him. Kapila opened his eyes, and the energy that poured from him instantly destroyed every one of them — reduced them to ash in a single moment.
Their bodies had never been given proper rites. Their ashes had never been touched by water. And so they could not reach heaven. They were trapped in Vaivasvata's eternal world — the realm of Yama, the god of death — unable to move on.
Only Ganga's water could save them. If her sacred stream touched their remains, they would be purified and released.
Bhagiratha had come to ask for that water.
Ganga was delighted with his words. She agreed to descend. But she told him something he had not expected.
"When I descend from the sky to the earth," she said, "my force will be difficult to bear. There is no one in the three worlds who can withstand it — except Nilakantha Maheshvara, the foremost among the gods."
Nilakantha — the blue-throated one. Maheshvara — the great lord. Shiva.
Ganga told Bhagiratha that he must go to Shiva, satisfy him through austerities, and obtain the boon that the god would bear her fall on his head. Only then could she descend safely. Only then could his fathers be saved.
Bhagiratha did not argue. He did not rest. He left immediately for Mount Kailasa. Aranyaka Parva, Chapter 404