The enlightened sage (Gurmukh) Basista, delivered the sermon about God (Hari). (Wadhans Ki Var M. 4, p. 591) Vasishtha is one of the most famous Indian sages. He was the author of several hymns of Rig Veda. In one of the hymns of the Rig Veda, he is called the son of Mitra and Varuna, bom from the mind of Urvashi. He was the preceptor of the king Dasaratha and on many occasions gave instructions to Rama, which are contained in YOGA VASISHTHA. It is said that he had the wish-fulfilling cow Nandini with him and Vishwamitra wanted to possess it, therefore there was a great animosity between the two sages.
Vishwamitra was a Kshatri and Vasishtha was a Brahmin. In order to possess Nandini, Vishwamitra wanted to become a Brahm-rishi like Vasishtha, but his royal pride stood in his way. In great ego, he even killed the sons of Vasishtha. But ultimately when he became modest and humble, Vasishtha assisted him and he became a Brahm-rishi. According to Manu, Vasishtha was one of the seven great rishis and also one of the ten prajapatis.
1. Kohli, Surindar Singh, Dictionary of Mythological References in Guru Granth Sahib, 1993