Srimad-Bhagavatam: Canto 9 - Chapter 1 - Verse 5-6
तस्य सत्यवतीं कन्यामृचीकोऽयाचत द्विज: ।वरं विसदृशं मत्वा गाधिर्भार्गवमब्रवीत् ॥ ५ ॥एकत: श्यामकर्णानां हयानां चन्द्रवर्चसाम् ।सहस्रं दीयतां शुल्कं कन्याया: कुशिका वयम् ॥ ६ ॥
tasya satyavatīṁ kanyāmṛcīko ’yācata dvijaḥvaraṁ visadṛśaṁ matvāgādhir bhārgavam abravīt
King Gādhi had a daughter named Satyavatī, whom a brāhmaṇa sage named Ṛcīka requested from the King to be his wife. King Gādhi, however, regarded Ṛcīka as an unfit husband for his daughter, and therefore he told the brāhmaṇa, “My dear sir, I belong to the dynasty of Kuśa. Because we are aristocratic kṣatriyas, you have to give some dowry for my daughter. Therefore, bring at least one thousand horses, each as brilliant as moonshine and each having one black ear, whether right or left.”
The son of King Gādhi was Viśvāmitra, who was said to be a brāhmaṇa and kṣatriya combined. Viśvāmitra attained the status of a brahmarṣi, as explained later. From the marriage of Satyavatī with Ṛcīka Muni would come a son with the spirit of a kṣatriya. King Gādhi demanded that an uncommon request be fulfilled before the brāhmaṇa Ṛcīka could marry his daughter.