Srimad-Bhagavatam: Canto 12 - Chapter 1 - Verse 61
Sanskrit:
वैशम्पायनशिष्या वै चरकाध्वर्यवोऽभवन् ।यच्चेरुर्ब्रह्महत्यांह: क्षपणं स्वगुरोर्व्रतम् ॥ ६१ ॥
ITRANS:
vaiśampāyana-śiṣyā vaicarakādhvaryavo ’bhavanyac cerur brahma-hatyāṁhaḥkṣapaṇaṁ sva-guror vratam
Translation:
The disciples of Vaiśampāyana became authorities in the Atharva Veda. They were known as the Carakas because they executed strict vows to free their guru from his sin of killing a brāhmaṇa.