Chandogya Upanishad 3.11

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:

'Yonder he neither rises nor sets at any time. If this is not true, ye gods, may I lose Brahman.'

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;.

This doctrine (beginning with III, 1, 1) Brahman (m. Hiranyagarbha) told to Pragâpati (Virâg), Pragâpati to Manu, Manu to his offspring (Ikshvâku, &c.) And the father told that (doctrine of) Brahman (n.) to Uddâlaka Âruni.

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.