Aśauca-vidhi (Rules of Impurity) within Śrāddha-kalpa — Chapter on Testing/Selecting Brahmanas and Honoring the Atithi
श्राद्धकल्पे भवेद्यस्तु सन्निपत्य तु पावनः / चतुर्दशानां विद्यानामेकस्यामपि पारगाः
śrāddhakalpe bhavedyastu sannipatya tu pāvanaḥ / caturdaśānāṃ vidyānāmekasyāmapi pāragāḥ
In the rite of śrāddha, one who assembles and becomes purifying should be accomplished in at least one of the fourteen sacred sciences.