Matsya Purana — Vrata-Ṣaṣṭhī: The Sixty Sacred Vows
दत्त्वा सितद्वितीयायाम् इन्दोर्लवणभाजनम् समान्ते गोप्रदो याति विप्राय शिवमन्दिरम् कल्पान्ते राजराजः स्यात् सोमव्रतमिदं स्मृतम् //
dattvā sitadvitīyāyām indorlavaṇabhājanam samānte goprado yāti viprāya śivamandiram kalpānte rājarājaḥ syāt somavratamidaṃ smṛtam //
On the second lunar day of the bright fortnight, having offered a vessel of salt to the Moon, and at the completion of the observance having also gifted a cow, one should go to a brāhmaṇa at a temple of Śiva. At the end of the aeon, he becomes a “king of kings”—this is remembered as the Soma‑vrata (Moon‑vow).
It does not describe pralaya directly; it uses the phrase “at the end of the kalpa” to express the long-term karmic fruit of the vow—sovereignty (rājarāja) accrued through ritual gifting and devotion.
It prescribes a householder-style dharma practice: observing a lunar-tithi vow, making specific donations (salt vessel, then cow), and honoring a brāhmaṇa at a Śiva temple—actions framed as producing merit and future rulership.
Ritually, it specifies Śukla-dvitīyā timing and a defined gift-sequence culminating at a Śiva temple; architecturally, it only implies temple-centered worship (śivamandira) rather than giving construction rules.