Khândogya Upanishad: IV, 13

THIRTEENTH KHANDA. 1. Then the Âhavanîya 3 fire taught him: 'Breath, ether, heaven, and lightning (these are my forms). The person that is seen in the lightning, I am he, I am he indeed. p. 67 2. 'He who knowing this meditates on him, destroys sin, obtains the world (of Agni Âhavanîya), reaches his full age, and lives long; his descendants do not perish. We guard him in this world and in the other, whosoever knowing this meditates on him.' 66:3 The Âhavanîya altar is the altar on the eastern side of the sacrificial ground.