[From Srila AC Bhaktivedanta Swami Prabhupada’s purport of CC Adi 7.72:]

Sri Bhaktisiddhanta Sarasvati Gosvami Maharaja comments…, “One can become perfectly successful in the mission of his life if he acts exactly according to the words he hears from the mouth of his spiritual master.” This acceptance of the words of the spiritual master is called srauta-vakya, which indicates that the disciple must carry out the spiritual master’s instructions without deviation. Srila Visvanatha Cakravarti Thakura remarks in this connection that a disciple must accept the words of his spiritual master as his life and soul.