Vishvamitra

Vishvamitra (Kaushika), son of king Gadhi of the Kushika line, is the one sage who, though born a kshatriya, attained brahmarshi rank by fierce austerity. His penance began with the episode of Vasishtha's wish-cow; the Menaka episode and the making of a separate heaven for Trishanku are among his famous narratives. He is held the seer of the Gayatri mantra and rishi of the Rigveda's third mandala, and it was he who gave Rama and Lakshmana the bala-atibala lore. At SB 1.9.7 he is present before Bhishma under the name Kaushika.

Śrīmad Bhāgavata Mahāpurāṇa 1.9.7 — Sanskrit Wikisource (pinned oldid=330834)