Bṛhadāraṇyaka Upaniṣad ("Great Forest Teaching") 3.3.2

3.3.2

sa hovācovācavai so'gacchanvai te tadyatrāśvamedhayājino gacchantīti kva nvaśvamedhayājino gacchantīti dvātrim̐śataṃ vai devarathāhnyānyayaṃ lokastam̐ samantaṃ pṛthivī dvistāvatparyeti tām̐ samantaṃ pṛthivīṃ dbistāvatsamudraḥ paryeti tadyāvatī kṣurasya dhārā yāvadvā makṣikāyāḥ patraṃ tāvānantareṇākāśastānindraḥ suparṇo bhūtvā vāyaveprāyacchattānvāyurātmani dhitvā tatrāgamayadyatrāśvamedhayājino'bhavannityevamivavai sa vāyumeva praśaśam̐ sa tasmādvāyureva vyaṣṭirvāyuḥ samaṣṭirapa punarmṛtyuṃ jayati ya evaṃ veda tato ha bhujyurlāhyāyanirupararāma

Yâgñavalkya said: 'He said to thee, I suppose, that they went where those go who have performed a horse-sacrifice.'
He said: 'And where do they go who have performed a horse-sacrifice?'
Yâgñavalkya replied: 'Thirty-two journeys of the car of the sun is this world. The earth surrounds it on every side, twice as large, and the ocean surrounds this earth on every side, twice as large. Now there is between them a space as large as the edge of a razor or the wing of a mosquito. Indra, having become a bird, handed them (through the space) to Vâyu (the air), and Vâyu (the air), holding them within himself, conveyed them to where they dwell who have performed a horse-sacrifice. Somewhat in this way did he praise Vâyu indeed. Therefore Vâyu (air) is everything by itself, and Vâyu is all things together. He who knows this, conquers death.' After that Bhugyu Lâhyâyani held his peace.

3.3.2.p1

iti tṛtīyādhyāye tṛtīyaṃ brāhmaṇam