The Bhagavata Purana narrates the following tale about Vishnu's Matsya incarnation (avatar):-
"Long ago, when life first appeared on the earth, a terrible demon terrorized the earth. He prevented sages from performing their rituals and stole the Holy Vedas, taking refuge in a conch shell in the depths of the ocean. Brahma, the creator of the world approached Vishnu for help and the latter immediately assumed the form of a fish and plunged into the ocean. He killed the demon by ripping open his stomach and retrieved the Vedas. Four forms emerged from the demon's stomach representing the four Vedas: Rig Veda, Sama Veda, Atharva Veda, and Yajur Veda."
