Śatapatha Brāhmaṇa ("of a hundred paths") 4.4.4.1

4.4.4.1

tāni vā etāni | nava samiṣṭayajūṃṣi juhoti tadyannava samiṣṭayajūṃṣi juhoti nava vā amūrbahiṣpavamāne stotriyā bhavanti saiṣobhayato nyūnā virāṭ prajananāyaitasmādvā ubhayato nyūnātprajananātprajāpatiḥ prajāḥ sasṛja itaścordhvā itaścāvācīstatho evaiṣa etasmādubhayata eva nyūnātprajananātprajāḥ sṛjata itaścordhvā itaścāvācīḥ

Now, it is nine Samishtayagus he offers on this occasion. The reason why he offers nine Samishtayagus is that those stotra-verses at the Bahishpavamâna chant amount to nine. Thus there is at both ends an inferior (incomplete) virâg, for the sake of production: it was from that same inferior (lower) source of production on both sides that Pragâpati produced the creatures,--from the one (he created) the upright, and from the other those tending to the ground. And in like manner does he (the Adhvaryu) now create creatures from that lower source of production on both sides,--from the one the upright, and from the other those tending to the ground.