Mahabharata 3.93.10

सरो गयशिरो यत्र पुण्या चैव महानदीऋषिजुष्टं सुपुण्यं तत्तीर्थं ब्रह्मसरोत्तमम्

saro gayaśiro yatra puṇyā caiva mahānadīṛṣijuṣṭaṃ supuṇyaṃ tattīrthaṃ brahmasarottamam

Our plain-language meaning of this verse is waiting for scholar review.