Emperor Sagara of Sūryavaṁśa (race descended from the sun) once started the Aśvamedha sacrifice (horse-sacrifice). When the sacrificial horse was lost, his sons went out in search of it and found it grazing in the monastery of the sage Kapila. The disrespect shown by them to the sage resulted in their being reduced to ashes. Aṁśumān the grandson of Sagara then set out in search of the horse and his uncles. When he discovered the horse and the tragedy, he pacified the sage and brought back the horse so that Sagara could complete the sacrifice without further hitch. After the completion of the sacrifice, Aṁśumān became the king and ruled for some time. Then he left his kingdom in charge of his son Dilīpa and retired to the forest to perform austerities. He tried to bring the river Gaṅgā to wash the ashes of his ancestors and redeem their souls, but he did not succeed. The task was achieved later by his grandson Bhagīratha.
See also BHAGĪRATHA.