Aśauca-vidhi (Rules of Impurity) within Śrāddha-kalpa — Chapter on Testing/Selecting Brahmanas and Honoring the Atithi
नार्हतस्तावपि श्राद्धे ब्रह्माणः क्रयविक्रयी / क्रयश्च विक्रयश्चैवाजीवितार्थे विगर्हितौ
nārhatastāvapi śrāddhe brahmāṇaḥ krayavikrayī / krayaśca vikrayaścaivājīvitārthe vigarhitau
In the śrāddha rite, brahmins engaged in buying and selling are not fit either, for purchase and sale done for livelihood are censured.