Srimad-Bhagavatam: Canto 9 - Chapter 1 - Verse 22
Sanskrit:
य: प्रियार्थमुतङ्कस्य धुन्धुनामासुरं बली ।सुतानामेकविंशत्या सहस्रैरहनद् वृत: ॥ २२ ॥
ITRANS:
yaḥ priyārtham utaṅkasyadhundhu-nāmāsuraṁ balīsutānām eka-viṁśatyāsahasrair ahanad vṛtaḥ
Translation:
To satisfy the sage Utaṅka, the greatly powerful Kuvalayāśva killed a demon named Dhundhu. He did this with the assistance of his twenty-one thousand sons.