Here is one Sanskrit passage traditionally associated with the Brahmastra:
वान्तं वह्निसमायुक्तं व्योमहालासमन्वितम् ।
मेषद्वयं दन्तयुतं हालाहलमतःपरम् ॥
घनाढ्यं वायुपूर्वं च दन्तयुक्तमथान्वितम् ।
सरं ऋक्षपर्यायं भान्तं भृगुमतःपरम् ॥
अम्बरं वायुसंयुक्तः अरिमर्दनमप्युतः ।
प्रदीप्तं अथ वक्तव्यं परमं च पदं ततः ॥
तदेते प्रयोक्तव्ये गायत्र्या मध्यमं ततः ।
पदत्रयं प्रयोक्तव्यं एतत् ब्रह्मास्त्रमीरितम् ॥
Meaning: It contains air, fire, and cosmic poison, two goat-like fangs, full of poison, weighty, emits air, contains mercury, fiery, sparkling, the sky is filled with air, enemy-killing, greatly radiant, and it is projected with three hymns, Gayatri at its centre, it is known as brahma-astra.
But don’t worry, you cannot invoke it just by reading these verses. The verses are highly technical and cryptic in their wording. Some people believe that these verses use symbolic or encoded terminology and compare them with the mantra-uddhāra traditions found in certain Tantric and Āgamic texts. However, there is no accepted scholarly consensus that this particular passage is an unsolved cryptographic code or that it can be mechanically decoded into an actual Brahmastra mantra. Most traditional interpretations treat it as a technical ritual instruction rather than a hidden code.
WHAT HAPPENS IF YOU TRY TO DECODE IT??
Quite a few interpretations have been proposed over the years, but none of them has been universally accepted. No traditional commentary or academic study has successfully demonstrated a definitive decoding that results in an operational mantra. So, as of today, the exact ritual significance of these verses remains uncertain. They remain among the most fascinating and technically complex passages associated with the Brahmastra.
But my question is, why do you wanna invoke Brahmastra in the first place??
NOTE: This answer is based on my research on this subject. If I have unintentionally made any mistakes, I sincerely seek forgiveness.
Hope this helps!
Jay SriRam!
ShriKrishnarpanamastu!