Vāsudeva’s Upadeśa: The Inner Enemy and the Indra–Vṛtra Precedent (आत्मशत्रु-बोधः; इन्द्र-वृत्रोपाख्यानम्)
ततो वृत्रं शरीरस्थं जघान भरतर्षभ । शतक्रतुरदृश्येन वज्ञेणेतीह न: श्रुतम्,भरतश्रेष्ठ! तत्पश्चात् शतक्रतुने अपने शरीरके भीतर स्थित हुए वृत्रासुरको अदृश्य वज्के द्वारा मार डाला ऐसा हमने सुना है
tato vṛtraṃ śarīrasthaṃ jaghāna bharatarṣabha | śatakratur adṛśyena vajreṇetīha naḥ śrutam ||
પછી, હે ભરતશ્રેષ્ઠ, શતક્રતુ (ઇન્દ્ર) એ પોતાના જ શરીરમાં સ્થિત થયેલા વૃત્રને—અહીં અમે જેમ સાંભળ્યું છે તેમ—અદૃશ્ય વજ્રથી સંહાર્યો.
वायुदेव उवाच
The verse uses the Indra–Vṛtra episode as an exemplum: when an obstructive force hides within oneself (symbolically, inner corruption or impediment to duty), it must be confronted and removed with resolute, dharma-aligned means, even if the remedy is subtle or not outwardly visible.
Vāyudeva reports a received tradition: Indra (Śatakratu) killed Vṛtra who was lodged within Indra’s own body, using an ‘unseen’ vajra (thunderbolt). The statement is framed as hearsay/authoritative tradition (“so we have heard”).