Śatapatha Brāhmaṇa ("of a hundred paths") 10.5.2.12

10.5.2.12

athādhyātmam yadetanmaṇḍalaṃ tapati yaścaiṣa rukma idaṃ tacuklamakṣannatha yadetadarcirdīpyate yaccaitatpuṣkaraparṇamidaṃ tatkṛṣṇamakṣannatha ya eṣa etasminmaṇḍale puruṣo yaścaiṣa hiraṇmayaḥ puruṣo'yameva sa yo'yaṃ dakṣiṇe'kṣanpuruṣaḥ

Therefore let him, who knows this, sleep, for it makes for heaven: he thereby, indeed, makes those two deities enjoy their dear wish, union. And one should not therefore forcibly awaken him who sleeps, lest he should hurt those two deities whilst enjoying their union; and hence the mouth of him who has been asleep is, as it were, clammy, for those two deities are then shedding seed, and from that seed everything here originates, whatsoever exists.