Adhyāya 2: Nārada’s Disclosure—Karṇa’s Training and the Brahmin’s Curse (Śānti-parva)
ब्र्मास्त्र ब्राह्मणो विद्याद् यथावच्चरितव्रत: । क्षत्रियो वा तपस्वी यो नान्यो विद्यात् कथंचन
brahmāstraṁ brāhmaṇo vidyād yathāvac caritavrataḥ | kṣatriyo vā tapasvī yo nānyo vidyāt kathaṁcana ||
“वत्स! ब्रह्मास्त्र को ठीक-ठीक वही ब्राह्मण जान सकता है जिसने यथावत् व्रत-आचरण (ब्रह्मचर्य आदि) का पालन किया हो, अथवा वह क्षत्रिय जो सच्चा तपस्वी हो। इसके सिवा कोई भी इसे किसी प्रकार नहीं सीख सकता।”
नारद उवाच
Extraordinary power (here, the Brahmāstra) is inseparable from ethical qualification: only one who has disciplined conduct and austerity—either a properly vowed Brahmin or an ascetic Kshatriya—may legitimately know it; mere curiosity or ambition is disqualifying.
Narada lays down a rule of eligibility for learning the Brahmāstra, emphasizing that such knowledge is restricted to those proven in vows and tapas, thereby warning against unfit transmission and misuse of destructive power.