Agniveshyagrihyasutra 3.1.1.1

3.1.1.1

amāvāsyāyāmaparāhṇe māsikam aparapakṣasya vāyukṣvahassu pitṛbhyo 'nnaṃ saṃskṛtya dakṣiṇāgrān darbhānāsanāni kalpayitvā brāhmaṇān śucīn mantravataḥ samāṅgānayugmānāmantrayate \

On the new-moon day in the afternoon, or on the uneven days of the dark fortnight [for] the monthly [śrāddha], having prepared food for the ancestors, having arranged seats of darbha grass pointing to the south, he invites Brahmins who are pure, proficient in mantras, without bodily defects, and an odd number in total.