Matsya Purana — The Attendant Hosts of the Sun and Moon: Monthly Gaṇas
ततस्तु शिशिरे चापि मासयोर्निवसन्ति ते त्वष्टा विष्णुर्जमदग्निर् विश्वामित्रस्तथैव च //
tatastu śiśire cāpi māsayornivasanti te tvaṣṭā viṣṇurjamadagnir viśvāmitrastathaiva ca //
Then, in the two months of the cold season (Śiśira) they dwell—namely Tvaṣṭṛ, Viṣṇu, Jamadagni, and likewise Viśvāmitra.
It does not describe Pralaya directly; it supports the Matsya Purana’s cosmological order by assigning specific deities and ṛṣis to seasonal months, implying a regulated cosmic rhythm rather than dissolution.
By identifying who presides over particular months of Śiśira, it implicitly guides proper seasonal observances—useful for householders planning vratas/rites and for kings organizing public rituals in harmony with sacred calendrical authority.
The verse is primarily calendrical, but it is ritually significant as a timing key: rites, offerings, and seasonal disciplines performed in Śiśira are traditionally aligned with the presiding powers named here rather than with Vastu or temple-measurement rules.