ज्ञात्वा तद्दानवेन्द्रस्य हयग्रीवस्य चेष्टितम् ।
दधार शफरीरूपं भगवान्हरिरीश्वरः ॥ ९ ॥
jnatva-after understanding; tat-that; danava-indrasya-of the great demon; hayagrivasya-of Hayagriva; cestitam-activity; dadhara-accepted; saphari-rupam-the form of a fish; bhagavan-the Supreme Personality of Godhead; harih-the Lord; isvarah-the supreme controller.
Understanding the acts of the great demon
Hayagriva, the Supreme Personality of Godhead,
Hari, who is full of all opulences, assumed the form of a fish and saved the Vedas by killing the demon.
Because everything was inundated by water, to save the Vedas it was necessary for the Lord to assume the form of a fish.