Maharshi Vasistha possessed a cow called Sabala who is able to give everything wished for. Once king Kaushika (Vishwamitra) saw the cow and wished to possess her. He asked Vasistha to hand her over but Vasistha refused to do so saying she actually belongs to Devas and not him. King Kaushika became angry and attacked Vasistha with all his forces. However, he was defeated by the power of his penance and was somehow rescued by Vamdeva. He asked Vamdeva, how can Vasistha defeat all his might on his alone. Vamdeva told him this happened due to Vasistha's Brahmashakti. Kaushika then wanted to become like Vasistha. Doing penance guided by Vamdeva, King Kaushika became Vishwamitra.