Srimad-Bhagavatam: Canto 12 - Chapter 1 - Verse 14

Sanskrit:

रक्षाच्युतावतारेहा विश्वस्यानु युगे युगे ।तिर्यङ्‌मर्त्यर्षिदेवेषु हन्यन्ते यैस्त्रयीद्विष: ॥ १४ ॥

ITRANS:

rakṣācyutāvatārehāviśvasyānu yuge yugetiryaṅ-martyarṣi-deveṣuhanyante yais trayī-dviṣaḥ

Translation:

In each age, the infallible Lord appears in this world among the animals, human beings, sages and demigods. By His activities in these incarnations He protects the universe and kills the enemies of Vedic culture.

Purport:

The protective activities of the Lord, indicated by the word rakṣā, constitute one of the ten fundamental topics of a Mahā-purāṇa, or a great Purāṇic literature.