The Vedas are texts that were developed over hundreds of years and are made up of hymns (samhita), ritualistic interpretations of hymns (Brahmanas), semi-metaphysical inquiries posed by thinkers who had renounced worldly life and lived in the forest (Aranyakas), and metaphysical explanations of rituals (Upanishads) contained in the Rig, Yajur, Sama and Atharva Vedas. 

One of the earliest descriptions of Being in the Upanishads can be found in the discussion between Ajatashatru and Gargya in the Brihadaranyaka Upanishad. Ajatashatru, the king of ancient Kashi, offered a thousand cows to Gargya, a brahmana, if he could provide a satisfactory explanation of Being. (Brahmanas refer to texts, as well as priests.) 

The Chandogya Upanishad provided one of the earliest descriptions of the return of the soul after death in the story of King Pravahana Jaivali’s instruction to a great sage, Uddalaka Aruni. This instruction was known as the doctrine of the five fires.