Aśauca-vidhi (Rules of Impurity) within Śrāddha-kalpa — Chapter on Testing/Selecting Brahmanas and Honoring the Atithi
ब्रह्मविक्रयिणस्तान्वै श्राद्धकर्मणि वर्जयेत् / न वियोगास्तु वेदानां यो नियुङ्क्ते स पापकृत्
brahmavikrayiṇastānvai śrāddhakarmaṇi varjayet / na viyogāstu vedānāṃ yo niyuṅkte sa pāpakṛt
Those who sell Brahma-vidyā—the Veda—should indeed be excluded from the śrāddha rite. Whoever enjoins ‘niyoga’ by sundering the Vedas is a doer of sin.