Khandogya-Upanishad: Third Prapathaka, Seventeenth Khanda
1. When a man (who is the sacrificer) hungers, thirsts, and abstains from pleasures, that is the Diksha (initiatory rite).
2. When a man eats, drinks, and enjoys pleasures, he does it with the Upasadas (the sacrificial days on which the sacrificer is allowed to partake of food).
3. When a man laughs, eats, and delights himself, he does it with the Stuta-sastras (hymns sung and recited at the sacrifices).
4. Penance, liberality, righteousness, kindness, truthfulness, these form his Dakshinas (gifts bestowed on priests, &c.)
5. Therefore when they say, “There will be a birth,” and “there has been a birth” (words used at the Soma-sacrifice, and really meaning, “He will pour out the Soma-juice,” and “he has poured out the Soma-juice”), that is his new birth. His death is the Avabhritha ceremony (when the sacrificial vessels are carried away to be cleansed).
6. Ghora Angirasa, after having communicated this (view of the sacrifice) to Krishna, the son of Devaki—and he never thirsted again (after other knowledge)—said: “Let a man, when his end approaches, take refuge with this Triad: ‘Thou art the imperishable, Thou art the unchangeable, Thou art the edge of Prâna.’” On this subject there are two Rik verses:—
7. “Then they see (within themselves) the ever-present light of the old seed (of the world, the Sat), the highest, which is lighted in the brilliant (Brahman).” [Rig-veda VIII, 6, 30]
“Perceiving above the darkness (of ignorance) the higher light (in the sun), as the higher light within the heart, the bright source (of light and life) among the gods, we have reached the highest light, yea, the highest light.” [Rig-veda I, 50, 10]