Matsya Purana — Glory of Prayaga: The Fruit of the Anashaka Fast and the Merit of the Yamuna
गङ्गा च यमुना चैव उभे तुल्यफले स्मृते केवलं ज्येष्ठभावेन गङ्गा सर्वत्र पूज्यते //
gaṅgā ca yamunā caiva ubhe tulyaphale smṛte kevalaṃ jyeṣṭhabhāvena gaṅgā sarvatra pūjyate //
The Gaṅgā and the Yamunā are both remembered as yielding equal spiritual merit; yet, solely because of her seniority, the Gaṅgā is worshipped everywhere.
This verse is not about Pralaya; it focuses on tirtha-mahātmyā—how sacred rivers confer spiritual merit and why Gaṅgā receives universal worship.
For householders (and kings setting public norms), it supports sustaining river-worship, pilgrimage, and purification rites—honoring both rivers’ merit while recognizing Gaṅgā’s traditional precedence.
Ritually, it implies bathing, offerings, and reverence at river-tīrthas; architecturally, it indirectly supports establishing ghāṭas and shrines at major rivers, with Gaṅgā given primary prominence due to tradition.