Khandogya-Upanishad: Eighth Prapathaka, Third Khanda
1. “These true desires, however, are hidden by what is false; though the desires be true, they have a covering which is false. Thus, whoever belonging to us has departed this life, him we cannot gain back, so that we should see him with our eyes.
2. “Those who belong to us, whether living or departed, and whatever else there is which we wish for and do not obtain, all that we find there (if we descend into our heart, where Brahman dwells, in the ether of the heart), There are all our true desires, but hidden by what is false. As people who do not know the country, walk again and again over a gold treasure that has been hidden somewhere in the earth and do not discover it, thus do all these creatures day after day go into the Brahma-world (they are merged in Brahman, while asleep), and yet do not discover it, because they are carried away by untruth (they do not come to themselves, i.e. they do not discover the true Self in Brahman, dwelling in the heart).
3. “That Self abides in the heart. And this is the etymological explanation. The heart is called hrid-ayam, instead of hridy-ayam, i.e. He who is in the heart. He who knows this, that He is in the heart, goes day by day (when in sushupti, deep sleep) into heaven (svarga), i.e. into the Brahman of the heart.
4. “Now that serene being which, after having risen from out this earthly body, and having reached the highest light (self-knowledge), appears in its true form, that is the Self,” thus he spoke (when asked by his pupils). This is the immortal, the fearless, this is Brahman. And of that Brahman the name is the True, Satyam,
5. This name Sattyam consists of three syllables, sat-ti-yam. Sat signifies the immortal, t, the mortal, and with yam he binds both. Because he binds both, the immortal and the mortal, therefore it is yam. He who knows this goes day by day into heaven (svarga).