Matsya Purana — Cosmic Architecture of Sun–Moon and the ‘Houses of the Gods’
तस्मात्ताम्रा भवन्त्यापो दिवारात्रिप्रवेशनात् अस्तं गते पुनः सूर्ये अहर्वै प्रविशत्य् अपः //
tasmāttāmrā bhavantyāpo divārātripraveśanāt astaṃ gate punaḥ sūrye aharvai praviśaty apaḥ //
Therefore the waters take on a coppery hue because they enter into day and night. And when the Sun has set, the day indeed passes into the waters again.
It does not describe Pralaya directly; it gives a cosmological account of how day and night operate in relation to the Sun and the waters, explaining observable changes (like a coppery tint) through the cyclical movement of time.
Indirectly, it supports dharmic time-awareness: householders and rulers schedule rituals, governance, and daily duties by the Sun’s cycle; the verse reinforces that day-night order is a cosmic principle to be followed in conduct and rites.
Ritually, it emphasizes Surya-based timing—sunrise/sunset as boundaries for acts like sandhyā and other observances; architecturally (Vastu), it supports orientation and planning aligned with solar movement, though no direct building rule is stated in this verse.