Shiva Purana
विश्वामित्रो गाधिसुतस्तपसैव महामुने ॥ क्षत्रियोऽथाभवद्विप्रः प्रसिद्धं त्रिभवेत्विदम् ॥ ५३ ॥
O great sage, the Kṣatriya king Viśvāmitra, the son of Gādhi, became a brahmin through penance. This is well known in the three worlds.
english translation
vizvAmitro gAdhisutastapasaiva mahAmune ॥ kSatriyo'thAbhavadvipraH prasiddhaM tribhavetvidam ॥ 53 ॥
hk transliteration by Sanscript