Khandogya-Upanishad: Third Prapathaka, Eleventh Khanda
1. When from thence he has risen upwards, he neither rises nor sets. He is alone, standing in the centre. And on this there is this verse:
2. “Yonder he neither rises nor sets at any time. If this is not true, ye gods, may I lose Brahman.”
3. And indeed to him who thus knows this Brahma-upanishad (the secret doctrine of the Veda) the sun does not rise and does not set. For him there is day, once and for all.
4. This doctrine (beginning with III, I, 1) Brahman (m. Hiranyagarbha) told to Pragâpati (Virig), Pragipati to Manu, Manu to his offspring (Ikshvaku, &c.) And the father told that (doctrine of) Brahman (n.) to Uddalaka Aruni.
5. A father may therefore tell that doctrine of Brahman to his eldest son, or to a worthy pupil.
But no one should tell it to anybody else, even if he gave him the whole sea-girt earth, full of treasure, for this doctrine is worth more than that, yea, it is worth more.