CHĀNDOGYA UPANISHAD · 8.6.3

तद् यत्रैतत् सुप्तः समस्तः संप्रसन्नः स्वप्नं न विजानाति ।
आसु तदा नाडीषु सृप्तो भवति ।
तं न कश्चन पाप्मा स्पृशति ।
तेजसा हि तदा संपन्नो भवति ॥

tad yatraitat suptaḥ samastaḥ saṃprasannaḥ svapnaṃ na vijānāti ।
āsu tadā nāḍīṣu sṛpto bhavati ।
taṃ na kaścana pāpmā spṛśati ।
tejasā hi tadā saṃpanno bhavati ॥

And when a man is asleep, reposing, and at perfect rest, so that he sees no dream, then he has entered into those arteries. Then no evil touches him, for he has obtained the light (of the sun).

F. Max Müller · The Upanishads, Sacred Books of the East 1 (1879)