Adhyāya 166: Kṛtaghna-doṣa (कृतघ्नदोषः) — the fault of ingratitude and the limits of expiation
गुरुतल्पमधिष्ठाय दुरात्मा पापचेतन: । स्त्रयाकारां प्रतिमां लिंग्य मृत्युना सोडभिशुद्धयति
Bhīṣma uvāca: gurutalpam adhiṣṭhāya durātmā pāpacetanaḥ | striy-ākārāṃ pratimāṃ liṅgya mṛtyunā so ’bhiśuddhyati ||
Bhīṣma said: A wicked man of sinful intent who has violated the teacher’s bed (i.e., committed adultery with the guru’s wife) becomes purified from that sin only by embracing a woman-shaped image (a heated iron effigy) and dying thereby. The passage presents an extreme expiatory rule meant to underscore the gravity of the offense against the guru’s household and the sanctity of dharma.
भीष्म उवाच
The verse stresses that violating the guru’s marital sanctity (gurutalpa) is among the gravest dharma-transgressions, and it frames purification as requiring an extreme, life-ending expiation—highlighting the seriousness of the offense and the ideal of uncompromising moral accountability.
In the Shanti Parva’s dharma instruction, Bhishma is describing prāyaścitta (expiatory discipline). Here he states a specific, severe expiation for the sin of approaching the guru’s bed—embracing a woman-shaped effigy (understood as heated iron) and dying, which is said to cleanse the sin.