As per Hindu tradition, it was King Bhagiratha’s austerities and desire to free the souls of his ancestors that brought Holy River Ganga from heaven to earth. One of the most important reasons why many people want to be cremated on the banks of Holy Ganga and want their ashes to be immersed in
Ganga is that they will attain Moksha or liberation from the cycle of birth and death.
The story of King Bhagiratha is found in a couple of Puranas, this is the one mentioned in the Narada Purana. Emperor Sagara had two wives – Keshini and Sumati. They were once offered two boons by Sage Aurva – first – an intelligent and pious son who will one day become a great king – second boon – sixty thousand sons.
Keshini opted for a single son and Sumati opted for sixty thousand sons.
The sixty thousands sons of Sumati created numerous troubles for the emperor. Indra and other devas, saints, and human beings were fed up with the troubles created by the sons.
Indra then approached Sage Kapila to find a solution. Sage Kapila to divert the attention of the sixty thousand sons in matters of kingdom, asked the king to perform an Ashwamedha Yaga.
In an Ashwamedha Yaga, the emperor releases a horse which travels through different kingdoms. Those kings who are ready to be a vassal of the emperor do not object the horse running through their kingdom. But those kings that are not ready to be a vassal stop the horse and then the issue is settled on the battleground.
The sixty thousand sons were following the horse released by Emperor Sagara. One day Indra stole the horse and hid it at the spot where Sage Kapila was meditating.
When the unruly sons discovered horse near Sage Kapila, they thought the saint had stolen it and started abusing and hitting him. Sage Kapila’s meditation was disturbed and the angry saint opened his eyes – reducing the sixty thousand sons into ashes. This spot is believed to the place where Ganga Sagar Mela is held annually – South of Kolkata – were Ganga merges with the Bay of Bengal.
Grandson of emperor Sagara reached the spot and prayed for forgiveness to Sage Kapila. The sage could not bring back the sons back but he said that they will attain Moksha when in future King Bhagiratha of the lineage will bring
Ganga down from heaven to earth.
After several generations, Bhagiratha was born in the family and he performed great austerities and impressed Brahma and Shiva.