Matsya Purana — The Greatness of Prayaga: Manasa Tirtha
अकामो वा सकामो वा गङ्गायां यो ऽभिपद्यते मृतस्तु लभते स्वर्गं नरकं च न पश्यति //
akāmo vā sakāmo vā gaṅgāyāṃ yo 'bhipadyate mṛtastu labhate svargaṃ narakaṃ ca na paśyati //
Whether one is free of desires or full of desires, whoever enters the Gaṅgā—upon death—attains heaven and does not behold hell.
This verse does not discuss pralaya; it focuses on tirtha-mahātmyā—how contact with the Ganga affects post-death destiny by removing the experience of naraka (hell).
It supports the dharmic ideal that rulers and householders should uphold and facilitate access to sacred rivers and pilgrimages; regardless of personal motive (desireless or desirous), approaching the Ganga is presented as a powerful meritorious act.
No direct Vastu or temple-architecture rule appears here; the ritual takeaway is the exceptional purifying status of the Ganga as a tirtha, implying practices like bathing, worship, and final rites near the river as highly meritorious.