Adhyāya 166: Kṛtaghna-doṣa (कृतघ्नदोषः) — the fault of ingratitude and the limits of expiation
ऊर्ध्व त्रिभ्योडपि वर्षेभ्यो यजेताग्निष्ठता परम् । ऋषभेैकसहसंर वा गा दत्त्वा शौचमाप्नुयात्
ūrdhvaṃ tribhyo 'pi varṣebhyo yajetāgniṣṭhata param | ṛṣabhaikasahasraṃ vā gā dattvā śaucam āpnuyāt ||
Bhīṣma said: After living in strict discipline for three full years, one should perform the Agniṣṭoma sacrifice as the highest expiation. Thereafter, by gifting a thousand bulls—or an equal number of cows—to Brāhmaṇas, a person attains purification. The teaching frames purification not as mere regret but as sustained self-restraint, followed by a solemn Vedic rite and generous restitution through charity.
भीष्म उवाच
Purification from serious fault is presented as a structured path: sustained self-restraint over time, completion of a major Vedic sacrifice (Agniṣṭoma), and substantial charitable giving (a thousand bulls or cows) to Brāhmaṇas—linking inner discipline, ritual responsibility, and social restitution.
In Bhīṣma’s instruction on dharma and expiation in the Śānti Parva, he prescribes a specific prāyaścitta: after a three-year period of disciplined living, the person should perform the Agniṣṭoma sacrifice and then donate a large number of cattle to Brāhmaṇas to regain śauca (purity).