SB 1.7.19
अस्त्रं ब्रह्मशिरो मेने आत्मत्राणं द्विजात्मजः ॥ १९ ॥
astraṁ brahma-śiro mene ātma-trāṇaṁ dvijātmajaḥ
Synonyms
yadā — when; aikṣata — he saw [or acknowledged (paryālocitavān)80]; śrānta-vājinam — that his horses were exhausted; ātmānam — [and] that he; aśaraṇam — was without any other refuge [or protector (rakṣaka-rahitam)81]; dvija-ātma-jaḥ — [Aśvatthāmā] the son of a brāhmaṇa [here the word dvijātmaja, meaning “one merely born from the body of a brāhmaṇa” (but not so in essence), implies his lack of foresight (dvijātmaja ity adīrgha-darśitvaṁ sūcitam)]; mene — considered [avābuddhayat82]; astram — the missile; brahma-śiraḥ — [that is] the weapon of Brahmā; ātma-trāṇam — as the only means to protect himself [ātma-rakṣopāyam].
Translation
When he saw that his horses were exhausted and that he was without any other refuge, Aśvatthāmā, the son of a brāhmaṇa, considered the missile weapon of Brahmā as the only means to protect himself.