Mahabharata 13.26.33
गङ्गाह्रद उपस्पृश्य तथा चैवोत्पलावनेअश्वमेधमवाप्नोति तत्र मासं कृतोदकः
gaṅgāhrada upaspṛśya tathā caivotpalāvaneaśvamedhamavāpnoti tatra māsaṃ kṛtodakaḥ
Our plain-language meaning of this verse is waiting for scholar review.
Open in the book