Chandogya Upanishad 8.11.1

8.11.1

tad yatraitat suptaḥ samastaḥ saṃprasannaḥ svapnaṃ na vijānātyeṣa ātmeti hovāca \
etad amṛtam abhayam etad brahmeti \
sa ha śāntahṛdayaḥ pravavrāja \
sa hāprāpyaiva devān etad bhayaṃ dadarśa \
nāha khalv ayam evaṃ saṃpraty ātmānaṃ jānāty ayam aham asmīti \
no evemāni bhūtāni \
vināśam evāpīto bhavati \
nāham atra bhogyaṃ paśyāmīti \\811.1\

Prajāpati said, ‘He who is fully asleep, composed, serene and knows no dream, he is the Ātman. He is the immortal, the fearless. He is Brahman.’ Indra went away satisfied in his heart. But even before reaching the gods he saw this difficulty: ‘In truth this one does not know himself now as “I am he”, nor indeed these beings. It seems as if he has gone to annihilation. I see no good in this.’