Hiranyakeshigrihyasutra 2.4.10.2

2.4.10.2

pitṛbhyonnaṃ saṃskṛtya dakṣiṇāgrāndarbhānāsanāni kalpayitvā brāhmaṇāñchucīnmantravataḥ samaṅgānayuja āmantrayate yonigotramantrāsaṃbandhān \2\

Having prepared food for the Fathers and having arranged southward-pointed Darbha grass as seats (for the Brâhmanas whom he is going to invite), he invites an odd number of pure Brâhmanas who are versed in the Mantras, with no deficient limbs, who are not connected with himself by consanguinity or by their Gotra or by the Mantras, (such as his teacher or his pupils).