Matsya Purana — Glory of Prayaga: The Fruit of the Anashaka Fast and the Merit of the Yamuna
येनैव निःसृता गङ्गा तेनैव यमुना गता योजनानां सहस्रेषु कीर्तनात्पापनाशिनी //
yenaiva niḥsṛtā gaṅgā tenaiva yamunā gatā yojanānāṃ sahasreṣu kīrtanātpāpanāśinī //
From the very source from which the Gaṅgā issued forth, from that same source the Yamunā too proceeded. Even from thousands of yojanas away, the mere recitation of her name and glory destroys sin.
It does not describe pralaya directly; it asserts sacred-geography theology—Gaṅgā and Yamunā share a common divine source, and their remembrance (kīrtana) removes sin even at great distance.
It supports accessible dharma: even when one cannot travel, a householder or ruler may gain purification through kīrtana—reverent recitation and remembrance of holy rivers—promoting inner discipline and ethical renewal.
Ritually, it highlights nāma-kīrtana as a valid purificatory practice; by implication it supports river-invocation in snāna, saṅkalpa, and daily rites, though it gives no direct Vāstu or temple-building rule.