Birth of Ganga is linked to Sagara, the king of Ayodhya. Though the king eagerly desired children, but had none. His elder wife was Keshini, and the second was Sumati, sister of Garuda. With his two wives, the king went to Himalaya to practice an austere penance. When a hundred years had passed, the rishi Brigu, whom he had honoured, granted him his wish. The rishi told him that one of his wives would bear a son who will perpetuate his race and the other shall give birth to sixty thousand sons. Thereafter the king revered the saint with circumambulation and obeisance and returned again to his city. In appropriate time, Keshini bore a son, and was named Asamanja and Sumati bore a gourd, and when it burst open the sixty thousand sons came out of it, whom the nurses fostered in jafs of ghee until they grew up to youth and beauty. But the eldest son, the child of Keshini, did not love his brothers and would cast them in the Sarayu River and watch them sink. Due to his evil disposition and for the wrongs he did to citizens and honest folk Asamanja was banished by his father. But he had a son named Suman who was fair-spoken to all and was well-beloved.

Sacrifice of Sagara
King Sagara once decided to organise a mighty yajna. The place was in the region between Himalaya and Vindhya. The horse was loosed there and Anshumat, a mighty chariot-fighter, followed to protect it. But it befell that a certain Vasava, assuming the form of a rakshasi, stole the horse away. Then the Brahmin priests informed the king and asked him to slay the thief and bring back the horse, otherwise the sacrifice would fail and misfortune would follow all concerned.

Sagara`s Sons Search For Horse
Sagara ordered his sixty thousand sons to seek the horse and all of them ranged the earth and when they did not find the horse upon its surface, they began to delve with hands like thunderbolts and mighty ploughshares, so that the earth cried out in pain. Great was the uproar of the serpents and the demons that were slain. For sixty thousand leagues they dug as if they would reach the very lowest deep. All the gods were frightened and informed Lord Brahma that the sons of Sagara are digging out the whole earth and many are slain and asked Brahma for help. Then Brahma replied that the earth was the consort of Vasudeva and he would take care of her.

After riving the entire earth, the sons returned to Sagara and informed him of the result, for they could not find the horse. But Sagara again commanded them to dig the earth and find the horse. They again plunged into the depths and came across the elephant Virupaksha, whom they worshipped and passed on. To the south they came next, to another mighty elephant, Mahapadma, like a mountain, bearing the earth upon his head; likely they came also to the western elephant named Saumanasa, and then to the north, where is Bhadra, white as snow, bearing the earth upon his brow.

The sons of Sagara came to the quarter east of north and found the eternal Vasudeva in the shape of Kapila, and hard by him they saw the horse browsing at his will. They rushed towards Kapila in fury and attacked him with trees and boulders, spades and ploughs, and addressed him as a thief who had stolen their horse. In response to the misdeeds of the sons of Sagara, Kapila uttered a dreadful roar and flashed a burning flame upon them that burned all of them to ashes.

Asamanja`s Son Suman Searches for His Uncles
After long time, no news of the sons of Sagara came to Ayodhya and Sagara ordered his grandson Suman, the son of Asamanj, to seek his uncles and learn their fate. Suman came across the elephants of east and south and west and north, and each assured him of success and at last he came across the heap of ashes that had been his uncles. He wailed there with heavy heart in bitter grief and there he also found the wandering horse. He wished to perform the funeral rites of his uncles but he could not find water anywhere. There he was informed by Garuda that his uncles were burned by Kapila and therefore, for their funeral, the water of the Ganga is required and then his uncles would reach Heaven. Then Garuda ordered Anshuman, as Suman was also called by this name, to take back the Horse and complete the sacrifice of his grandfather and the same was politely obeyed by him and the sacrifice was successfully completed.

Bhagiratha`s Prayer to Brahma
Anshuman became the king of Ayodhya after the death of Sagara and after ruling the kingdom for several years he left it to his son and went to the Himalayas and from there he also went to the Heaven. His son, King Dilipa, constantly pondered over the way to bring down Ganga so that the ashes might be purified and the sons of Sagara attain to the Heaven. After thirty thousand years he died, and his son Bhagiratha, a royal saint, followed him. He consigned the kingdom to the care of a counselor and went to the Himalayan forests, performing terrible austerities for a thousand years to draw down Ganga from the skies. Lord Brahma was pleased by his devotion and granted him a boon. Bhagiratha asked for the washing down of the ashes of the sons of Sagara by the waters of Ganga and than he should beget a son. Brahma blessed Bhagiratha and told him that in order to bring Ganga to earth; he should pray Lord Shiva to hold the flow of Ganga from the heaven for the earth would not be able to bear her force when she would fall upon it.

Bhagiratha worshipped Lord Shiva for many years, and Mahadeva was pleased and undertook to bear the daughter of the Himalayas, and received the river upon his head. Then Ganga, in mighty torrent, cast herself down from Heaven on to the gracious head of Shiva. But when Ganga fell on the tangled locks of Shiva, she was unable to reach the earth, but wandered there unable to escape for several years. Then Bhagiratha again engaged in many hard austerities, till Shiva would set the river free and Ganga fell in seven streams, three to the east, three to the west, while one followed the car of Bhagiratha.

As Ganga followed Bhagiratha, she flooded the sacrificial ground of the puissant Jahna, and he was greatly angered, and in his wrath he drank up all her wondrous waters.Then the deities besought and prayed him to set the Ganga free, till he relented and released her through his ears, and again she followed the car of Bhagiratha. At last she came to the mighty river Ocean and plunged into the nether regions; there she laved the heap of ashes, and the sixty thousand sons of Sagara, the king of Ayodhya, were cleansed of every sin and attained to Heaven. Thus, the birth of Ganga or the arrival of Ganga in the earth from the heaven took place due to the hard work of Bhagiratha and Ganga was also named after her disciple Bhagiratha and called Bhagirathi.