Dasakam 032 - Sloka 01

पुरा हयग्रीवमहासुरेण षष्ठान्तरान्तोद्यदकाण्डकल्पे । निद्रोन्मुखब्रह्ममुखात् हृतेषु वेदेष्वधित्स: किल मत्स्यरूपम् ॥१॥

पुराlong agoहयग्रीव-महा-असुरेणby Hayagreeva, the great Asuraषष्ठ-अन्तरान्त-उद्यत्-at the end of the sixth Manvantaraअकाण्ड-कल्पेin the Naimittika Pralayaनिद्रा-उन्मुख-ब्रह्म-मुखात्-from the mouth of Brahmaa who was about to sleepहृतेषु वेदेषु-when the Vedas were stolenअधित्स: किल(Thou) desired to assumeमत्स्य-रूपम्the form of a Fish

Long ago during the Pralaya which took place at the end of the sixth Manvantara, when Brahmaa was about to sleep, the great Asura Hayagreeva stole the Vedas from his mouth. In order to restore them, Thou decided to incarnate as a fish.