Vishnupurana 4.4.20

4.4.20

taṃ cāha bhagavān uktam evaitan mayā pautras te tridivād gaṅgāṃ bhuvam ānayiṣyatīti |
tadambhasā saṃspṛṣṭeṣv asthibhasmasv ete svargam ārokṣyanti |
bhagavadviṣṇupādāṅguṣṭhavinirgatasya jalasya hi tanmāhātmyam ||

When Sagara learned that his sons, whom he had sent in pursuit of the sacrificial steed, had been destroyed by the might of the great Rishi Kapila, he dispatched Anśumat, the son of Asamaujas, to effect the animals recovery. The youth, proceeding by the deep path which the princes had dug, arrived where Kapila was, and bowing respectfully, prayed to him, and so propitiated him, that the saint said, "Go, my son, deliver the horse to your grandfather; and demand a boon; thy grandson shall bring down the river of heaven on the earth." Anśumat requested as a boon that his uncles, who had perished through the sage's displeasure, might, although unworthy of it, be raised to heaven through his favour. "I have told you," replied Kapila, "that your grandson shall bring down upon earth the Ganges of the gods; and when her waters shall wash the bones and ashes of thy grandfather's sons, they shall be raised to Swarga. Such is the efficacy of the stream that flows from the toe of Vishńu, that it confers heaven upon all who bathe in it designedly, or who even become accidentally immersed in it: those even shall obtain Swarga, whose bones, skin, fibres, hair, or any other part, shall be left after death upon the earth which is contiguous to the Ganges." Having acknowledged reverentially the kindness of the sage, Anśumat returned to his grandfather, and delivered to him the horse. Sagara, on recovering the steed, completed his sacrifice; and in affectionate memory of his sons, denominated Ságara the chasm which they had dug.