Chandogya Upanishad is associated with the Kauthuma Shakha of the Sama Veda. It is part of the Chandogya Brahmana, which has ten chapters. The Chandogya Upanishad comprises of eight chapters, and commences on the Om Mantra. Chandogya Upanishad is the part of Chandogya Brahaman that contains ten chapters. The 10th Khanda of first chapter deals with the story of Ushasti. According to it, once, the crops of the Kurus were destroyed due to thunderstorms. Ushasti the son of Chakra, along with his wife and child shifted to another village that belonged to a man who owned an elephant. They lived in a deplorable condition. Ushasti once begged food from the owner of the elephant who was then eating some beans. The man replied that he had nothing to give apart from the beans he was eating. Ushasti then asked for those beans and the man gave him his food. The man also offered him the water that he had left after drinking. Ushasti however, did not accept it saying that he would not drink the water that has been left by someone. He had only accepted the beans as it was required to satisfy his hunger but can manage water from some other place.
After eating the beans Ushasti gave few to his wife that was left. She kept the beans aside as she had already before. The next morning when Ushasti got up she gave him the beans to eat. Having eaten the food he then went to attend a sacrifice organised by a king. The king has chosen him to perform all the priestly offices. Ushasti arrived at the sacrificial ceremony and saw the udgatri priests have assembled there. He went and sat beside them in a place where they would recite the hymns. Ushasti told the prastotri priest that if he recites the Prastiva without being aware of the deity that belongs to Prastiva, his head would then fall off. In the same way he also addressed the udgatri priest that if he would recite the Udgitha without knowing the deity then his head would fall off. He next told the pratihartri priest that he must recite the Pratihara only after knowing the deity that belongs to the Pratihara else his head would also fall off. Upon hearing Ushasti all the priests stopped performing their duties and sat in silence. Ushasti then explained each of them about their concerned deities. He told the prastotri priest that its deity is the Prana. All beings evolve from the Prana and then merge into it. Hr next explained the udgatri priest that its deity is the Sun. all beings praise the Sun that is the source of light. Finally Ushasti explained the pratihartri priest that its deity is the food. All beings take food to survive. All the priests now fully aware of the deities began performing the sacrifice.
