Srimad-Bhagavatam: Canto 1 - Chapter 1 - Verse 38
Sanskrit:
प्रतिश्रुतं च भवता पाञ्चाल्यै शृण्वतो मम ।आहरिष्ये शिरस्तस्य यस्ते मानिनि पुत्रहा ॥ ३८ ॥
ITRANS:
pratiśrutaṁ ca bhavatāpāñcālyai śṛṇvato mamaāhariṣye śiras tasyayas te mānini putra-hā
Translation:
Furthermore, I have personally heard you promise Draupadī that you would bring forth the head of the killer of her sons.