Matsya Purana — Vrata-Ṣaṣṭhī: The Sixty Sacred Vows
सप्तरात्रोषितो दद्याद् घृतकुम्भं द्विजातये घृतव्रतमिदं प्राहुर् ब्रह्मलोकफलप्रदम् //
saptarātroṣito dadyād ghṛtakumbhaṃ dvijātaye ghṛtavratamidaṃ prāhur brahmalokaphalapradam //
After observing (the vow) for seven nights, one should give a pot filled with clarified butter (ghee) to a twice-born (Brāhmaṇa). This is declared to be the “ghee-vow” (ghṛta-vrata), bestowing the fruit of attaining Brahma-loka.
It does not discuss Pralaya directly; it teaches a dharma practice (a seven-night observance followed by ghee-donation) whose stated spiritual result is attainment of Brahma-loka.
It frames an actionable dāna-vrata: after maintaining discipline for seven nights, a householder (and likewise a king as dharma-protector) should support the twice-born through a prescribed gift—here, a ghee-filled pot—linking social duty (support of ritual specialists) with promised spiritual merit.
The ritual takeaway is the specific vrata procedure and dāna item: completing a seven-night observance and donating a ghṛta-kumbha (pot of ghee), a common ritual substance used for homa, lamps, and offerings.