King Kaushika and His Transformation Into Viswamithra

Once there lived a powerful king named Kaushika. 

One day, the king and his men went for a hunting expedition. It became dark and the king and his army was in the middle of the forest. They moved across the thick woods and reached the hermitage of Sage Vasishta. 

Sage Vasishta welcomed the king and army. He respectfully asked the king and his men to be his guest. However king Kaushika was proud. He laughed on the sage saying, 'O Sage! How would you feed me and my entire army?'

Another sage Agasthya who lived in the same hermitage, called a cow called Nandini. 

Nandini was the daughter of the heavenly cow Kamadhenu. 

Sage Agastha prayed to mother cow Nandini to give food for king Kaushika and his army. Mother cow Nandini accepted sage request. She gave adundant food. The king and his army enjoyed the food to their heart content. 

Seeing the wonder of cow Nandini, king Kaushika said, 'Sage Vasishta! This cow is wonderful. It should be with a king like me, so that I can give food to several hungry and destitude people to come to me. There is no use of it being with you. I request you to give this cow to me for the benefit of masses'.

Sage Vasishta humbly replied, 'This cow came to our hermitage on its own. It has come to serve the sages of this hermitage. O King! We cannot give this holy animal to you!'

Hearing Vasishta, king Kaushika became very angry. He began attacking the sage without any thought.

Sage Vasishta took his holy stick and planted it before him. The stick defended the sage from furious attack. At last king Kaushika gave up. He returned with his army - unthankful and angry.

After returning to his kingdom, king Kaustik gave up his riches and palace life. He gave his kingdom to his sons and renounced the kingly 

life. He performed severe penance for years.

After years of penance, Lord Brahma pleased with king Kausti appeared before him and said, 'Kaushik, your are a powerful king. You have performed severe penance and I am pleased with it. Ask me what you want'.

Kaushik replied, 'O mighty Brahma! I have renounced the worldly life. I want to become a sage like Vasishta'.

Lord Brahma replied, 'O king! You were born in kingly clan. So you cannot become Brahma sage like Vasishta. However, I can grant you boon to become a kingly sage (raja rishi)'.

King Kaushik became a raja rishi. He continued performing penance for several years, until he was granted the boon to become a Brahma rishi like Vasishta. After he became brahma rishi, he came to be know as Viswamithra (the friend of the universe).