Vishwamitra was one of the seven rishis. He was born a Kshatriya who was accepted as a Brahmin because of his intense meditations. He occupied a very important position in the RigVeda and he is associated with the famous Gayatri Mantra.
The disputes between Vishwamitra and Vashishta are told in the Puranas. Once Vishwamitra went to the ashram of Vashishta. He was treated royally and every desire of his was met. Still, he coveted Vashitha’s cow Kamadhenu which granted all material desires. He tempted her with much treasure, but she refused to accompany him. He tried to take her by force with his soldiers but Kamadhenu conjured up more soldiers. Vashistha entered the fray with his hundred sons. A battle ensued which Vishwamitra roundly lost. He determined to become Vashishta’s equal trhough prayers and penance.
While he was engaged in these penances, he became connected to a certain prince who had been banished for twelve years by his father because he had tried to ravish a woman of good virtue. While in exile, the prince lived with and took care of Vishwamitra. Once during a terrible storm, the prince was undergoing a silent fast, and the sage himself was praying. Kamadhenu the cow came by. Such was their craving that they overcame the magical cow and killed her. Vashitha was disgusted and gave the prince the name Trisankhu which means guilty of three sins ; the sin for which he was in exile;the sin of breaking one’s avowed penance and the sin of killing a cow.
Vishwamitra agreed to give him a boon and he asked to be admitted into the heavens. Vishwamitra granted his request as he himself had become a rishi through his severe austerities but Vashistha would not agree. While the two went through long arguments, poor Trishanku was left nowhere, neither a prince,nor a sage, nor allowed to enter the heavens. Eventually Brahma reconciled the two rishis explaining how each had arrived at their views through ardent penance, and both could live in the Cosmic order. Vishwamitra was Rama’s guru when he went to the Swayamvar which Raja Janak arranged for his daughter Sita. In one of their battles they
cursed each other to become birds and plucked out each others eyes and feathers. Then Brahma intervened and forced them to accept each other as equals.