Kauṣītaki Upaniṣad 2.5.2-5

2.5.2

yāvad vai puruṣo bhāṣate na tāvat prāṇituṃ śaknoti /

As long, verily, as a person is speaking, he is not able to breathe. Then he is sacrificing breath (_prāṇa_) in speech.

2.5.3

prāṇaṃ tadā vāci juhoti /

2.5.4

yāvad vai puruṣaḥ prāṇiti na tāvad bhāṣituṃ śaknoti /

As long, verily, as a person is breathing, he is not able to speak. Then he is sacrificing speech (_vāc_) in breath.

2.5.5

vācaṃ tadā prāṇe juhoti /