Mahabharata 12.49.28

12.49.28

viśvāmitraṃ ca dāyādaṃ gādhiḥ kuśikanandanaḥ |
prāpa brahmarṣisamitaṃ viśvena brahmaṇā yutam || 28 ||

"Vasudeva continued, 'Then Satyavati brought forth a son in Bhrigu's race who was devoted to penances and characterised by tranquil pursuits, viz., Jamadagni of regulated vows. Kusika's son Gadhi begot a son named Viswamitra. Possessed of every attribute of a Brahmana, that son (though born in the Kshatriya order) was equal to a Brahmana. Richika (thus) begot Jamadagni, that ocean of penances. Jamadagni begot a son of fierce deeds. The foremost of men, that son mastered the sciences, including the science of arms. Like unto a blazing fire, that son was Rama, the exterminator of the Kshatriyas. Having gratified Mahadeva on the mountains of Gandhamadana, he begged weapons of that great god, especially the axe of fierce energy in his hands. In consequence of that unrivalled axe of fiery splendour and irresistible sharpness, he became unrivalled on earth. Meanwhile the mighty son of Kritavirya, viz., Arjuna of the Kshatriya order and ruler of the Haihayas, endued with great energy, highly virtuous in behaviour, and possessed of a thousand arms through the grace of (the great Rishi) Dattatreya, having subjugated in battle, by the might of his own arms, the whole earth with her mountains and seven islands, became a very powerful emperor and (at last)