Aśauca-vidhi (Rules of Impurity) within Śrāddha-kalpa — Chapter on Testing/Selecting Brahmanas and Honoring the Atithi
यथावद्वर्त्तमानाश्च सर्वे ते पङ्क्तिपावनाः / असंदेहस्तु सौपर्णाः पञ्चाग्नेयाश्च सामगाः
yathāvadvarttamānāśca sarve te paṅktipāvanāḥ / asaṃdehastu sauparṇāḥ pañcāgneyāśca sāmagāḥ
All who conduct themselves according to rule are purifiers of the ritual row; without doubt they are Sauparṇas, established in the five-fire observance, and chanters of the Sāma.