Śatapatha Brāhmaṇa ("of a hundred paths") 7.4.2.40

7.4.2.40

tadāhuḥ | kasmādabhisvayamātṛṇamanyā iṣṭakā upadhīyante prācya etā iti dve vai yonī iti brūyāddevayoniranyo manuṣyayoniranyaḥ prācīnaprajananā vai devāḥ pratīcīnaprajananā manuṣyāstadyadetāḥ prācīrupadadhāti devayonerevaitadyajamānam prajanayati

Here now they say, 'Why are those other bricks placed in front of the naturally-perforated one?' Let him say, There are two wombs (birthplaces)--the one being the womb of the gods, the other the womb of men: the gods have their birthplace in the east, and men in the west; and when he lays down those (bricks) in front, he thereby causes the Sacrificer to be born from the womb of the gods.