Jaiminīya Upaniṣad Brāhmaṇa 2.1.18

2.1.18

te prāṇenodgātrādīkṣanta
sa yad eva prāṇena prāṇiti tad ātmana āgāyad atha ya itare kāmās tān devebhyaḥ /

They consecrated themselves with breath as the udgātṛ. Whatever one breathes with breath, that he sang for himself, but whatever other desires there were, those [he sang] for the gods.