Explanation:

  rishi vishwamitra- Brahmarshi Vishvamitra (visva-mitra) is one of the most venerated rishis or sages of ancient India. He is also credited as the author of most of Mandala 3 of the Rigveda, including Gayatri Mantra. The Puranas mention that only 24 rishis since antiquity have understood the whole meaning of—and thus wielded the whole power of—Gayatri Mantra. Vishvamitra is supposed to be the first, and Yajnavalkya the last.

rishi vashishta-  Vasishtha is a revered Vedic sage in Hinduism. He is one of the Saptarishis (seven great Rishis) of India. Vasishtha is credited as the chief author of Mandala 7 of Rigveda. Vasishtha and his family are mentioned in Rigvedic verse ,other Rigvedic mandalas and in many Vedic texts. His ideas have been influential and he was called as the first sage of the Vedanta school of Hindu philosophy by Adi Shankara.