Chandogya Upanishad is one of the oldest Upanishad written on the Vedic Brahmana period about ninth to eighth century BC. Chandogya Upanishad is associated with Sama Veda. It is ranked ninth in the Muktika canon of hundred and eight Upanishadas. The 3rd Khanda of Chapter Eight of Chandogya Upanishad states about the serene Self and Satya Brahman. According to it all true desires are covered by what is false. Though they always exist, these have a false covering. Thus, one belonging to the embodied creature has departed from this life is never again beheld in this world. All the people that belong to a person whether they are dead or alive or any desire that he wishes for and does not achieve, finds them all within his own Self. All the true desires rest there. Like many people who remain ignorant of the spot where the treasure of gold has been hidden in the earth and walk over it again and again without finding it, so does all the creatures daily retire to this world of Brahman and yet do not find it as they are misled by untruth.
This real Self abides in the heart. This one i.e. ayam is in the heart i.e. hridi. Hence it is known as hridyayam. Therefore he who knows it daily retires to the region of svarga (heaven) in his heart. He who knows this everyday retires to the region of heaven i.e. Brahman, dwelling within the heart. A person who realises this rises from this body and attains a noble body of light or the Highest Light and finally reaches his own true form. This highest form is the Self, it is immortal and fearless. It is the real Brahman. Of this Brahma the real name is satya (truth). The Brahman is indicated by three syllable, Sat, ti and yam. That which is Sat signifies the Immortal; and that which is ti is the mortal; and yam binds them both. The syllable binds both, therefore it is called yam. He who knows this everyday retires into the world of Heaven i.e. Brahman, dwelling in the heart.
