Śrīmad-Bhāgavatam · Text 8.24.9
Who is speaking and story frame
ज्ञात्वा तद् दानवेन्द्रस्य हयग्रीवस्य चेष्टितम् ।
दधार शफरीरूपं भगवान् हरिरीश्वर: ॥ ९ ॥
jñātvā tad dānavendrasya
hayagrīvasya ceṣṭitam
dadhāra śapharī-rūpaṁ
bhagavān harir īśvaraḥ
Understanding the acts of the great demon Hayagrīva, 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.
Read Śrīla Prabhupāda's purport on Vedabase.io