Aśauca-vidhi (Rules of Impurity) within Śrāddha-kalpa — Chapter on Testing/Selecting Brahmanas and Honoring the Atithi
बार्हस्पत्ये महाशास्त्रे यश्च पारङ्गतो द्विजः / सर्वे ते पावना विप्राः पङ्क्तीनां समुदात्दृताः
bārhaspatye mahāśāstre yaśca pāraṅgato dvijaḥ / sarve te pāvanā viprāḥ paṅktīnāṃ samudātdṛtāḥ
The twice-born who is well-versed in the great Bārhaspatya śāstra—all such vipras are purifying and are to be received with honor in the ritual rows.