Matsya Purana — Solar Dynasty Prelude: Vivasvān–Saṃjñā–Chāyā
ततः स भगवान्गत्वा भूर्लोकम् अमराधिपः कामयामास कामार्तो मुख एव दिवाकरः //
tataḥ sa bhagavāngatvā bhūrlokam amarādhipaḥ kāmayāmāsa kāmārto mukha eva divākaraḥ //
Then that blessed lord, sovereign of the immortals, went to the earthly world; and the Sun—his very face—was seized by longing and desired.
This verse does not describe Pralaya directly; it presents a mythic-cosmic scene where divine powers move through realms and desire (kāma) arises, a common Purāṇic way to explain subsequent events in the cosmos.
Indirectly, it functions as a moral subtext: even exalted beings can be disturbed by desire, implying that householders and rulers should govern kāma through dharma and self-restraint to avoid disorder.
No explicit Vāstu/ritual rule is stated in this verse; its key takeaway is symbolic—Divākara (the Sun) as a divine ‘face’—which later traditions may connect to solar worship, timing of rites, and auspicious observances, but not to a specific architectural injunction here.