Srimad-Bhagavatam: Canto 10 - Chapter 1 - Verse 21

Sanskrit:

य एतस्मिन् महाभागे प्रीतिं कुर्वन्ति मानवा:। नारयोऽभिभवन्त्येतान् विष्णुपक्षानिवासुरा: ॥ २१ ॥

ITRANS:

ya etasmin mahā-bhāgeprītiṁ kurvanti mānavāḥnārayo ’bhibhavanty etānviṣṇu-pakṣān ivāsurāḥ

Translation:

Demons cannot harm the demigods, who always have Lord Viṣṇu on their side. Similarly, any person or group attached to all-auspicious Kṛṣṇa cannot be defeated by enemies.

Purport:

Śrīla Prabhupāda has especially indicated in this connection that just as Lord Kṛṣṇa’s associates could not be defeated by Kaṁsa, so His modern-day devotees will not be defeated by their demoniac opponents, nor will the Lord’s devotees be defeated by the internal enemies — the lusty, materialistic senses.