Matsya Purana — Solar Dynasty Prelude: Vivasvān–Saṃjñā–Chāyā
यमश्च यमुना चैव यमलौ तु बभूवतुः ततस्तेजोमयं रूपम् असहन्ती विवस्वतः //
yamaśca yamunā caiva yamalau tu babhūvatuḥ tatastejomayaṃ rūpam asahantī vivasvataḥ //
Thus were born the twins—Yama and Yamunā. Thereafter, being unable to endure the blazing, radiant form of Vivasvān (the Sun), (she) withdrew in search of relief.
This verse is genealogical rather than pralaya-focused: it records the birth of the twins Yama and Yamunā and highlights the unbearable solar radiance of Vivasvān, a motif used to explain subsequent events in the lineage narrative.
By introducing Yama—associated with dharma, restraint, and moral order—the verse indirectly frames the ethical backdrop of kingship and household life: rule and conduct are measured against dharma, for which Yama becomes a cosmic exemplar and enforcer in later tradition.
No direct Vāstu or temple-rule instruction appears in this verse; its ritual takeaway is indirect—invocation of solar brilliance (tejas) and deities like Sūrya/Yama often underlies later rites, but this line itself is primarily narrative-genealogical.