Bṛhadāraṇyaka Upaniṣad ("Great Forest Teaching") 6.2.15

6.2.15

te ya evametadvidurye cāmī araṇye śraddhām̐ satyamupāsate te'rcirabhisaṃbhavantyarciṣo'harahna āpūryamāṇapakṣamāpūryamāṇapakṣādyānṣaṇmāsānudaṅṅāditya eti māsebhyo devalokaṃ devalokādādityamādityādvaidyutaṃ tānvaidyutānpuruṣo mānasa etya brahmalokāngamayati te teṣu brahmalokeṣu parāḥparāvato vasanti teṣāṃ na punarāvṛttiḥ

'Those who thus know this (even Grihasthas), and those who in the forest worship faith and the True (Brahman Hiranyagarbha), go to light (arkis), from light to day, from day to the increasing half, from the increasing half to the six months when the sun goes to the north, from those six months to the world of the Devas (Devaloka), from the world of the Devas to the sun, from the sun to the place of lightning. When they have thus reached the place of lightning a spirit comes near them, and leads them to the worlds of the (conditioned) Brahman. In these worlds of Brahman they dwell exalted for ages. There is no returning for them.