Matsya Purana — Dynastic Genealogies: Paurava–Anu Lines
गो ऽभ्याहते तमसि वै गौतमस्तु ततो ऽभवत् काक्षीवांस्तु ततो गत्वा सह पित्रा गिरिव्रजम् //
go 'bhyāhate tamasi vai gautamastu tato 'bhavat kākṣīvāṃstu tato gatvā saha pitrā girivrajam //
When the darkness was struck down by the Cow, then Gautama was born. Thereafter Kākṣīvān went, together with his father, to Girivraja.
This verse is not about pralaya; it functions as a genealogical notice, marking the birth of Gautama and the movement of Kākṣīvān to Girivraja.
Indirectly, it supports dharma by anchoring social memory in lineage and place—key Purāṇic tools for legitimizing royal/householder traditions through recognized sages and sacred geography.
No explicit Vāstu or ritual rule appears; the only practical takeaway is geographical—Girivraja is named as an important settlement/stronghold in Purāṇic tradition.