Furthermore, I have personally heard you promise Draupadī that you would bring forth the head of the killer of her sons.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
प्रतिश्रुतं च भवता पाञ्चाल्यै शृण्वतो मम । आहरिष्ये शिरस्तस्य यस्ते मानिनि पुत्रहा
pratiśrutaṃ ca bhavatā pāñcālyai śṛṇvato mama | āhariṣye śirastasya yaste mānini putrahā
SB 1.7.38