Jaiminīya Upaniṣad Brāhmaṇa 3.8.2

3.8.2

atha ha sma vai yaḥ purā brahmavādyaṃ vadaty anyatarām upāgād iti ha smainam manyante
atho ha smainam mṛtam ivaivopāsate /

For in ancient times, when anyone engaged in a theological disputation, they thought: "He has undertaken one or the other [survival or destruction]."
And they treated him as if he were already dead.