Chāndogya Upaniṣad 1.3.1

1.3.1

athādhi(S ) \
ya evāsau tapati tam udgītham upāsīta \
udyan vā eṣa prajābhya udgāyati \
udyaṃs tamo bhayam apahanti \
apahantā ha vai bhayasya tamaso bhavati ya evaṃ veda \\103.1\

1. Now with reference to the divinities.— Him who glows yonder [i.e. the sun] one should reverence as an Udgītha. Verily, on rising (ud-yan), he sings aloud (ud-gāyati) for creatures. On rising, he dispels darkness and fear. He, verily, who knows this becomes a dispeller of fear and darkness.