Khandogya-Upanishad: Fourth Prapathaka, Twelfth Khanda

1. Then the Anvaharya fire taught him: “Water, the quarters, the stars, the moon (these are my forms). The person that is seen in the moon, I am he, I am he indeed.

2. “He who knowing this meditates on him, destroys sin, obtains the world (of Agni Anvaharya), 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.”