Once King Vishwamitra was traveling with his huge army. He stopped at the hermitage of Sage Vashishta. Sage Vashishta provided a big feast for the whole army. Astounded by this, King Vishwamitra asked sage about this food. Sage Vashishta told him about Kamdhenu wishing the cow.
King Vishwamitra, who was amazed by her powers, asked sage Vashistha to give Kamdhenu in exchange for gold and jewels but sage Vashistha refused.
King Vishwamitra tried to take Kamadhenu by force and ordered his soldiers to seize Kamdhenu. After sage Vashishta’s permission, Kamadhenu created an army of warriors to defend herself. Her army annihilated Vishwamitra’s army and killed his sons.
King Vishwamitra then attacked sage Vashishta with his celestial weapons but the sage Vashishta was so calm and he neutralized every weapon with his spiritual knowledge. Then king Vishwamitra realized that his weapon power was useless against the spiritual power of sage Vashishta.
After this defeat King Vishmamitra understood the power of spiritual knowledge and undertook thousands of years of severe penance and also became the highest order of sage which is known as Brahmarishi.