Srimad-Bhagavatam: Canto 9 - Chapter 1 - Verse 14
Sanskrit:
पुनर्जाता यजस्वेति स प्रत्याहाथ सोऽब्रवीत् ।सान्नाहिको यदा राजन् राजन्योऽथ पशु: शुचि: ॥ १४ ॥
ITRANS:
punar jātā yajasvetisa pratyāhātha so ’bravītsānnāhiko yadā rājanrājanyo ’tha paśuḥ śuciḥ
Translation:
When the teeth grew in again, Varuṇa came and said to Hariścandra, “Now you can perform the sacrifice.” But Hariścandra then said, “O King, when the sacrificial animal becomes a kṣatriya and is able to shield himself to fight with the enemy, then he will be purified.”