Śatapatha Brāhmaṇa ("of a hundred paths") 6.7.2.7

6.7.2.7

taṃ vā etam | atra pakṣapucavantaṃ vikaroti yādṛgvai yonau reto vikriyate tādṛgjāyate tadyadetamatra pakṣapucavantaṃ vikaroti tasmādeṣo 'mutra pakṣapucavānjāyate

He fashions him here (in the pan or womb) into (a bird) with wings and tail; for whatlike the seed is fashioned in the womb, suchlike it is born; and because he here fashions him as (a bird) with wings and tail, therefore he is hereafter born with wings and tail.