Brihadaranyaka-Upanishad: Fifth Adhyâya, Third Brahmana
1. Pragâpatii is the heart, is this Brahman, is all this. The heart, hridaya, consists of three syllables. One syllable is hri, and to him who knows this, his own people and others bring offerings. One syllable is da, and to him who knows this, his own people and others bring gifts. One syllable is yam and he who knows this, goes to heaven (svarga) as his world.