Kauṣītaki Upaniṣad 2.13.15

2.13.15

te vāyupraviṣṭā ākāśātmānaḥ svar īyuḥ /

All those divinities, verily, having recognized the superior excellence in the vital breath, and having passed into the vital breath, even the intelligential self (prajñātman), went forth from this body —all these together. They, having entered into the wind, having the nature of space (ākāśātman), went to heaven (svar).