Srimad-Bhagavatam: Canto 1 - Chapter 1 - Verse 15
Sanskrit:
यद्यप्यस्त्रं ब्रह्मशिरस्त्वमोघं चाप्रतिक्रियम् ।वैष्णवं तेज आसाद्य समशाम्यद् भृगूद्वह ॥ १५ ॥
ITRANS:
yadyapy astraṁ brahma-śirastv amoghaṁ cāpratikriyamvaiṣṇavaṁ teja āsādyasamaśāmyad bhṛgūdvaha
Translation:
O Śaunaka, glory of Bhṛgu’s family, although the supreme brahmāstra weapon released by Aśvatthāmā was irresistible and without check or counteraction, it was neutralized and foiled when confronted by the strength of Viṣṇu [Lord Kṛṣṇa].
Purport:
In the Bhagavad-gītā it is said that the brahmajyoti, or the glowing transcendental effulgence, is resting on Lord Śrī Kṛṣṇa. In other words, the glowing effulgence known as brahma-tejas is nothing but the rays of the Lord, just as the sun rays are rays of the sun disc. So this Brahma weapon also, although materially irresistible, could not surpass the supreme strength of the Lord. The weapon called brahmāstra, released by Aśvatthāmā, was neutralized and foiled by Lord Śrī Kṛṣṇa by His own energy; that is to say, He did not wait for any other’s help because He is absolute.