Story of Sage Raikva occurs in Chandogya Upanishad (IV – 1). His meeting with King Janashruti and the conversation is of great importance. King Janashruti was famous for his generosity and took pride in the fact. Once the king was resting on the terrace of his palace and he overheard the conversation between two flamingos.
One flamingo was admonishing the other for crossing the bright light of fame of King Janashruti.
The other flamingo told that King Janashruti was not the meritorious person on land. There was a poor cart man who had found peace with himself. He is the meritorious person.
The king set out to search for Raikva and found him in a remote village.
The king approached the cart man with numerous gifts of cattle and gold in return of knowledge.
Raikva declined the gifts saying that material wealth could not buy spiritual knowledge.
The king gave up his royal pride and requested Raikva to impart knowledge of the Supreme Reality.
Raikva then imparts knowledge to King Janashruti and it can be found in the Chandogya Upanishad.