The Upanishads, Part 1 (SBE01), by Max Müller, , at sacred-texts.com
1. After that the Gârhapatya fire 4 taught him Earth, fire, food, and the sun (these are my forms, or
forms of Brahman). The person that is seen in the sun, I am he, I am he indeed 1.
2. 'He who knowing this meditates on him, destroys sin, obtains the world (of Agni Gârhapatya), 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.'
65:4 The household altar.
66:1 Fanciful similarities and relations between the fires of the three altars and their various forms and manifestations are pointed out by the commentator. Thus earth and food are represented as warmed and boiled by the fire. The sun is said to give warmth and light like the fire of the altar. The chief point, however, is that in all of them Brahman is manifested.