Matsya Purana — The Greatness of Prayaga: Manasa Tirtha
मानसं नाम तत्तीर्थं गङ्गाया उत्तरे तटे त्रिरात्रोपोषितो भूत्वा सर्वकामानवाप्नुयात् //
mānasaṃ nāma tattīrthaṃ gaṅgāyā uttare taṭe trirātropoṣito bhūtvā sarvakāmānavāpnuyāt //
There is a sacred ford named Mānasā on the northern bank of the Gaṅgā. Having observed a fast there for three nights, one attains the fulfillment of all desired aims.
This verse is not about pralaya; it belongs to a tīrtha-māhātmya passage, emphasizing the spiritual efficacy (phala) of fasting at a specific Gaṅgā tīrtha.
It recommends a disciplined vow (three-night fast) at a sacred place—an actionable dharmic practice for householders and rulers alike, aligning personal desires with ritual restraint and pilgrimage merit.
The ritual point is trirātra-upavāsa (a three-night fast) performed at Mānasā Tīrtha on the Gaṅgā’s northern bank; no vastu/temple-building rule is stated in this verse.