This story of Ganga's descent was narrated by Rishi Lomasha to Yudhishthira during the latter's pilgrimage (Mahabharata, Vana Parva, Tirthayatra Parva)

King Bhagiratha brings Ganga to fill the empty ocean

There was born in the family of the Ikshvakus, a ruler of the earth named Sagara, endued with beauty, and strength. That same king of a dreaded name was sonless! He carried havoc through the tribes of the Haihayas and the Talajanghas; brought under subjection the whole of the military caste; and so ruled over his own kingdom. He had two wives proud of their beauty and of their youth, one a princess of the Vidarbha race, and the other of the royal line of Sibi. That same ruler of men, betook himself to the mountain Kailasa, accompanied by both his wives, and with the desire of having a son became engaged in the practice of exceeding austere penances. Being engaged in the practice of rigid austerities, and also employed in the contemplation known by the name of Yoga, he obtained the sight of the magnanimous god with three eyes, the slayer of the demon called Tripura; the worker of blessings for all beings; the eternally existent one; the ruling Being, the holder of the Pinaka bow; carrying in his hand his well-known weapon, the trident; the god of three eyes; the repository of  eternal peace; the ruler of all those that are fierce; capable of assuming very many forms; and the lord of the goddess Uma. That same ruler of men, of mighty arms, as soon as he beheld the god fell down at his feet, with both his queens, and proffered a prayer to have a son. The god Shiva, well pleased with him, spoke thus to that most righteous of the rulers of men, attended by his two wives, saying, “O lord of men! considering the astrological moment at which you have proffered your prayer to me, sixty thousand sons, most valorous and characterised by exceeding pride, will be born in one off your two wives here. But they all shall perish together. In the other wife, however, will be born a single valiant son, who will perpetuate your race.” Having said this to him, the god Rudra vanished from sight at that very spot, and that same king Sagara now came back to his own abode accompanied by his two wives, exceedingly delighted at heart for what had happened then.

There the two wives of him, the princess of Vidarbha and the princess of Sibi, came erelong to be with child. Afterwards, on the due day, the princess of Vidarbha brought forth something of the shape of a gourd and the princess of Sibi gave birth to a boy as beautiful as a god. Then the ruler of the earth made up his mind to throw away the gourd, when he heard proceeding from the sky a speech uttered in a grave and solemn voice, “O king! do you not be guilty of this hasty act; you should not abandon your sons. Take out the seeds from the gourd and let them be preserved with care in steaming vessels partly filled with clarified butter. Then you will get sixty thousand sons. The great god Shiva has spoken that your sons are to be born in this manner. Let not therefore your mind be turned away therefrom.”

When he heard these words proceeding from the sky, he had faith therein, and did all that he was directed to do! Then Sagara took separately each of the seeds and then placed these divisions of the gourd in vessels filled with clarified butter. Intent on the preservation of his sons, he provided a nurse for every receptacle. Then after a long time there arose sixty thousand exceedingly powerful sons of that same king, they were born to that saint-like king, by Rudra's favour. They were terrible; and their acts were ruthless. They were able to ascend and roam about in the sky; and being numerous themselves, despised everybody, including the gods. They would chase even the gods, the Gandharvas, and the Rakshasas and all the born beings, being themselves valiant and addicted to fighting. Then all people, harassed by the dull-headed sons of Sagara, united with all the gods, went to Brahma as their refuge. Then addressed the blessed grandfather of all beings Brahma, “Go you your way, you gods, together with all these men. In a not very long space of time, there will come about a great and exceedingly terrible destruction of Sagara's sons, caused by the deed perpetrated by them.” Thus addressed, those same gods, and men, bade adieu to the grandfather, and went back to whence they had come.

Then after the expiry of very many days, the mighty king Sagara accepted the consecration for performing the rites of a horse-sacrifice. His horse began to roam over the world, protected by his sons. When the horse reached the sea, waterless and frightful to behold, although the horse was guarded with very great care, it suddenly vanished at the very spot it stood upon. Then, those same sons of Sagara imagined the same fine horse to have been stolen; and returning to their father, narrated how it had been stolen out of sight. Thereupon he addressed them, saying, “Go you and search for the horse in all the cardinal points.” Then, by this command of their father, they began to search for the horse in the cardinal points and throughout the whole surface of the earth. But all those sons of Sagara, all mutually united, could not find the horse, nor the person who had stolen it. Coming back then, they with joined palms thus addressed their father, standing before them, “O Protector of men! By your command, the whole of this world with its hills and its forest tracts, with its seas, and its woods, and its islands, with its rivulets and rivers and caves, has been searched through by us. But we cannot find either the horse, or the thief who had stolen the same.” Hearing the words, the same king became senseless with wrath, and then told them all, carried away by Destiny, “Go you all, may you never return! Search you again for the horse. Without that sacrificial horse, you must never return, my boys!”

And those same sons of Sagara, accepted this command of their father, and once more began to search through the entire world. Now these heroes saw a rift on the surface of the earth. Having reached this pit, the sons of Sagara began to excavate it. With spades and pickaxes they went on digging the sea, making the utmost efforts. That same abode of Varuna namely the ocean, being thus, excavated by the united sons of Sagara and rent and cut on all sides round, was placed in a condition of the utmost distress. The demons and snakes and Rakshasas and various other animated beings began to utter distressful cries, while being killed by Sagara's sons. Hundreds and thousands of animated beings were beheld with severed heads and separated trunks and with their skins and bones and joints rent asunder and broken. Thus they went on digging the ocean, which was the abode of Varuna and an exceedingly long space of time expired in this work, but still the horse was not found. Then, towards the north-eastern region of the sea, the incensed sons of Sagara dug down as far as the lower world, and there they beheld the horse, roaming about on the surface of the ground. They saw the magnanimous Kapila, who looked like a perfect mass of splendour. Having beheld him shining with his brightness, just as the fire shines with its flames, they, seeing the horse, were flushed with delight. They being incensed, sent forward by their fate, paid no heed to the presence of the magnanimous Kapila, and ran forward with a view to seizing the horse. Then, Kapila, the most righteous of saints, he whom the great sages name as Kapila Vasudeva, assumed a fiery look, and the mighty saint shot flames towards them, and thereby burnt down the dull-headed sons of Sagara.

Narada, whose practice of austerities was very great, when he beheld them reduced to ashes, came to Sagara's side, and gave the information to him. When the king learnt this terrible news which proceeded from the mouth of the saint, for nearly an hour he remained sad, and then he bethought himself of what Shiva had said. Then sending for Amshuman, the son of Asamanjas, and his own grandson, he, spoke the following words, “Those same sixty thousand sons of unmeasured strength having encountered Kapila's wrath, have met their death on my account. O my boy of stainless character! your father also has been forsaken by me, in order to discharge my duty as a king, and being desirous of doing good to my subjects.”

A son was born to Sagara, known by the name of Asamanjas, he who was given birth to by the princess of Sibi. He used to seize by throat the feeble children of the townsmen, and threw them while screaming into the river. Thereupon the townsmen, overwhelmed with terror and grief, met together, and all standing with joined palms, besought Sagara in the following way, “O great king! You are our protector from the dreaded peril of attack from a hostile force. Therefore it is proper for you to deliver us from the frightful danger, proceeding from Asamanjas.” The most righteous of the rulers of men, having heard this frightful news from his subjects, for nearly an hour remained sad and then spoke to his ministers, saying, “This day from the city let my son Asamanjas be driven forth. If you wish to do what will be acceptable to me, let this be quickly done.” Those same ministers, thus addressed by the king, performed in a hurry exactly what the king had commanded them to do. Thus the magnanimous Sagara banished his son, with a view to the welfare of the residents of the town. Amshuman was Asamanjasa’s powerful son.

Sagara said, “O my boy! Sore am I at heart for having abandoned your father, on account of the death of my sons, and also on being unsuccessful in getting back the horse. Therefore, O grandson! harassed with grief and confounded with the obstruction to my religious rites as I am, you must bring back the horse and deliver me from hell.” Thus addressed by the magnanimous Sagara, Amshuman went with sorrow to that spot where the earth had been excavated. By that very passage he entered into the sea, and beheld that illustrious Kapila and that same horse. Having beheld that ancient saint, most righteous of his order, looking like a mass of light, he bowed with his head to the ground, and informed him of the reason of his visit. Then Kapila was pleased with Amshuman, and that saint of a virtuous soul told him to ask for a favour from him. He in the first place prayed for the horse, for the purpose of using it in the sacrifice; in the second place he prayed for the purification of his fathers. Then the mighty chief of saints, Kapila spoke to him, saying, “I shall grant you everything that you desire. May good luck be yours! In you are fixed the virtues of forbearance, truth, and righteousness. By you has Sagara had all his desires fulfilled. You are really a son to your father. By your ability the sons of Sagara will go to heaven, will be delivered from the consequences of their unhallowed death. The son of your son, with a view to purifying the sons of Sagara, will obtain the favour of the great god Shiva, by means of practising great austerities, and will thus bring to this world the river that flows in three separate streams, Ganga. May good luck be yours! Take you with you the sacrificial horse. Finish the sacrificial rites of the magnanimous Sagara.”

Thus addressed by the illustrious Kapila, Amshuman took the horse with him, and came back to the sacrificial yard of the mighty-minded Sagara. Then he fell prostrate at the feet of the high-souled Sagara, who smelt him on the head and narrated all the events to him, all that had been seen and heard by him, and likewise the destruction of Sagara's sons. He also announced that the horse had been brought back to the sacrificial yard. When king Sagara heard of this, he no more grieved on account of his sons. He praised and honoured Amshuman, and finished those same sacrificial rites. His sacrifice finished, Sagara was greeted honourably by all the gods; and he converted the sea, Varuna's dwelling place, into a son of himself. King Sagara having ruled his kingdom for a period of exceeding length, placed his grandson on the throne, full of responsibilities and then ascended to heaven.

Amshuman likewise, ruled over the world as far as the edge of the sea, following the foot-prints of his father's father. His son was named Dilipa, versed in virtue. Upon him placing the duties of his sovereign post, Amshuman like-wise departed this life. Then when Dilipa heard what an awful fate had overtaken his forefathers, he was sorely grieved and thought of the means of raising them. The ruler of men made every great effort towards the descent of Ganga to the mortal world. But although trying to the utmost of his power, he could not bring about what he so much wished. A son was born to him, known by the name of Bhagiratha beauteous, and devoted to a virtuous life, and truthful, and free from feelings of malice. Dilipa appointed him as king, and betook himself to the forest life. That same king Dilipa, devoted himself to a successful course of austerities, and at the end of sufficient period, from the forest departed to heaven.

That same king, of a powerful bow, possessing every great fighting power became the delight of the eyes and the soul of all the world. He of the powerful arm came to learn how his forefathers had met an awful end from Kapila of mighty soul, and how they had been unable to attain the region of gods. He with a sorrowful heart made over his kingly duties to his minister, and, for practising austerities, went to the side of the snowy Mountain the Himalayas. Desirous of extinguishing his sins by leading an austere life, and thereby obtaining the favour of the goddess Ganga, he visited that foremost of mountains, Himalaya. He beheld it adorned with peaks of diverse forms full of mineral earth; besprinkled on all sides with drops from clouds which were resting themselves upon the breeze; beautiful with rivers and groves and rocky spurs, looking like so many palaces in a city; attended upon by lions and tigers that had concealed themselves in its caves and pits; and also inhabited by birds of checkered forms, which were uttering diverse sounds, such as the Bhringarajas, and ganders, and Datyuhas, and water-cocks, and peacocks and birds with a hundred feathers, and Jivanjivakas, and black birds, and Chakoras of eyes furnished with black corners, and the birds that love their young. He saw the mountain abounding in lotus plants growing in delightful reservoirs of water. The cranes rendered it charming with their sounds; and the Kinnaras and the celestial nymphs were seated on its stony slabs. The elephants occupying the cardinal points had everywhere robbed its trees with the end of their tusks; and the demi-gods of the Vidyadhara class frequented the hill. It was full of various gems, and was also infested by snakes bearing terrible poison and of glowing tongues. The mountain at places looked like massive gold, and elsewhere it resembled a silvery pile, and at some places it was like a sable heap of collyrium. Such was the snowy hill where the king now found himself. That most praiseworyour of men at that spot betook himself to an awful austere course of life. For one thousand years his subsistence was nothing but water, fruit and roots. When, however, a thousand years according to the calculation of gods had elapsed, then the great river Ganga having assumed a material form, manifested to him her divine self.

Ganga said. “O great king! what do you desire of me? And what must I bestow on you? Tell me the same! I shall do as you may ask me.” Thus addressed, the king then made his reply to Ganga, the daughter of the snowy Hill, saying, “O great river! my father's fathers, while searching for the horse, were sent by Kapila to the abode of the god of death. Those same sixty thousand sons of Sagara of mighty soul, having met with the majestic Kapila, perished, in an instant of time. Having thus perished, there has been no place for them in the region of heaven. So long as you do not besprinkle those same bodies with your water, there is no salvation for these same Sagara's sons. Carry you my forefathers, Sagara's sons, to the region of heaven. On their account am I beseeching you forsooth.”

Ganga, the goddess saluted by the world, having heard these words of the king, was well pleased, and spoke to Bhagiratha the following words: “O great king! I am prepared to do what you do ask me; there is no doubt therein. But when I shall descend from the sky to the earth, the force of my fall will be difficult to sustain. In the three worlds there exists none who is able to sustain the same, excepting Shiva, the most praiseworthy of gods, the great Lord with the throat of sable blue. Obtain the favour, by practising austerities, of that same Shiva, giver of boons. That same god will sustain my descent upon his head. Your desire he will fulfill, the desire, namely, to be of service to your fathers, O king!” Then the great king Bhagiratha having heard the same, went to the Kailasa hill, and betaking himself to a severe course of penances, at the expiration of a certain length of time obtained the favour of that worker of blessings Shiva. That same best of men, in order that his forefathers might have a place in heaven secured to them, received from that very Shiva the fulfilment of his wish, namely the wish that the descending Ganga might be sustained.

The blessed God having heard what Bhagiratha had said, and with a view to doing what was agreeable to the residents of heaven, replied to the king, saying, “So let it be. For your sake I shall sustain the river of the gods, when she will take her descent from the sky, she who is pure and blessed and divine!” Saying this, he came to the snowy mountain, surrounded by his attendants, of awful mien, and with uplifted weapons of diverse forms. Standing there, he said to Bhagiratha, the most praiseworyour of men, “O prince of a powerful arm! do you pray to the river, the daughter of the king of mountains. I shall sustain that most praiseworthy of rivers when she falls down from the third region of the world heaven.” Having heard these words uttered by Shiva, the king became devout in heart, made obesiance and directed his thoughts towards Ganga. Then the delightful river, of pure water in being so thought of by the king, and seeing that the great lord Shiva was standing to receive her fall, came down all of a sudden from the sky. Seeing that she had taken her leap from the sky, the gods, together with the mighty saints, the Gandharvas, the snakes, and the Yakshas, assembled there as spectators. Then came down from the sky Ganga, the daughter of the snowy mountain. Her whirlpools were raging, and she was teeming with fishes and sharks. She directing her course towards the sea, separated herself, into three streams; and her water was bestrewn with piles of froth, which looked like so many rows of white ganders. Crooked and tortuous in the movement of her body, at places; and at others stumbling at it were; and covered with foam as with a robe: she went forward like a woman drunk. Elsewhere, by virtue of the roar of her waters, she uttered loud sounds. Thus assuming very many different aspects, when she fell from the sky, and reached the surface of the earth, she said to Bhagiratha, “O great king! show me the path that I shall have to take. For your sake have I descended to the earth.” Having heard these words, king Bhagiratha directed his course towards the spot where lay those bodies of mighty Sagara's sons, in order that the holy water might flood the same. Having achieved the task of sustaining Ganga, Shiva, saluted by men, went to Kailasa the most praiseworthy of mountains, accompanied by the celestials. The protector of men Bhagiratha accompanied by Ganga reached the sea; and the sea, the abode of Varuna, was quickly filled. The king adopted Ganga as a daughter of himself, and at that spot offered libations of water to the names of his forefathers; thus was his heart's wish fulfilled. Thus Ganga, running in three streams, was brought down to the earth for filling the sea; which had been drunk up by the mighty seer Agastya.