Matsya Purana — The Glory of Prayaga: Pilgrimage
अधर्मेणावृतो लोको नैव गच्छति तत्पदम् स्वल्पमल्पतरं पापं यदा ते स्यान्नराधिप प्रयागं स्मरमाणस्य सर्वमायाति संक्षयम् //
adharmeṇāvṛto loko naiva gacchati tatpadam svalpamalpataraṃ pāpaṃ yadā te syānnarādhipa prayāgaṃ smaramāṇasya sarvamāyāti saṃkṣayam //
A world veiled by unrighteousness does not reach that supreme state. Yet, O king, when even a small—indeed, the slightest—sin arises in you, by merely remembering Prayāga it all comes to complete destruction.
It does not discuss pralaya; it teaches a moral-spiritual principle: adharma blocks attainment of the highest state, while the sacred power of Prayaga (even by remembrance) is said to exhaust sins.
Addressing a “narādhipa,” it warns that adharma prevents reaching the supreme goal; it also recommends tirtha-smaraṇa (remembering a sacred place) as a purificatory aid—supporting a ruler’s duty to remain morally clean and uphold dharma.
No vastu/temple-building rule is stated; the ritual takeaway is tirtha-smaraṇa: remembering Prayaga itself is presented as a powerful act of purification.