Matsya Purana — Cosmic Architecture of Sun–Moon and the ‘Houses of the Gods’
उदिते तु पुनः सूर्ये ऊष्माग्नेस्तु समाविशत् पादेन तेजसश्चाग्नेस् तस्मात् संतपते दिवा //
udite tu punaḥ sūrye ūṣmāgnestu samāviśat pādena tejasaścāgnes tasmāt saṃtapate divā //
But when the Sun rises again, the fire of heat enters it—indeed, a quarter portion of Agni’s radiance; therefore, by day the world becomes scorched.
It explains a cosmological mechanism (Agni/tejas entering the Sun as heat) rather than a direct Pralaya event, grounding how heat operates in the ordered cosmos between cycles.
Indirectly, it supports dharmic governance and household discipline by emphasizing predictable natural law—daytime heat as a cosmic function—informing daily routines, protection of people, and timing of work and rites.
While not a direct Vastu rule, it underlines the ritual and practical importance of solar timing (day/heat), relevant to scheduling ceremonies and to Vastu considerations like orientation and heat management in dwellings and temples.