Kauṣītaki Upaniṣad 2.5.8

2.5.8

etad dha vai pūrve vidvāṃso 'gnihotraṃ na juhavāñ cakruḥ //5//

These two are unending, immortal oblations; whether waking or sleeping, one is sacrificing continuously, uninterruptedly. Now, whatever other oblations there are, they are limited, for they consist of works (_karma-maya_). Knowing this very thing, verily, indeed, the ancients did not sacrifice the Agnihotra sacrifice.